Sorry for crying "fixed" though it still doesn't work. It worked only once after
rebooting to 2.6.15-9-k7, and now results again in "error, ports already in use".

Here the kernel.log from the one time, where everythink was ok:

Dec 20 15:48:55 localhost kernel: Inspecting /boot/System.map-2.6.15-9-k7
Dec 20 15:48:56 localhost kernel: Loaded 22896 symbols from
/boot/System.map-2.6.15-9-k7.
Dec 20 15:48:56 localhost kernel: Symbols match kernel version 2.6.15.
Dec 20 15:48:56 localhost kernel: No module symbols loaded - kernel modules not
enabled. 
Dec 20 15:48:56 localhost kernel: ] Mount-cache hash table entries: 512
Dec 20 15:48:56 localhost kernel: [4294671.581000] CPU: After generic identify,
caps: 0383f9ff c1cbf9ff 00000000 00000000 00000000 00000000 00000000
Dec 20 15:48:56 localhost kernel: [4294671.581000] CPU: After vendor identify,
caps: 0383f9ff c1cbf9ff 00000000 00000000 00000000 00000000 00000000
Dec 20 15:48:56 localhost kernel: [4294671.581000] CPU: L1 I Cache: 64K (64
bytes/line), D cache 64K (64 bytes/line)
Dec 20 15:48:56 localhost kernel: [4294671.581000] CPU: L2 Cache: 64K (64
bytes/line)
Dec 20 15:48:56 localhost kernel: [4294671.581000] CPU: After all inits, caps:
0383f9ff c1cbf9ff 00000000 00000020 00000000 00000000 00000000
Dec 20 15:48:56 localhost kernel: [4294671.581000] mtrr: v2.0 (20020519)
Dec 20 15:48:56 localhost kernel: [4294671.581000] Enabling fast FPU save and
restore... done.
Dec 20 15:48:56 localhost kernel: [4294671.581000] Enabling unmasked SIMD FPU
exception support... done.
Dec 20 15:48:56 localhost kernel: [4294671.581000] Checking 'hlt' instruction... OK.
Dec 20 15:48:56 localhost kernel: [4294671.585000] checking if image is
initramfs... it is
Dec 20 15:48:56 localhost kernel: [4294672.331000] Freeing initrd memory: 5962k
freed
Dec 20 15:48:56 localhost kernel: [4294672.338000]  not found!
Dec 20 15:48:56 localhost kernel: [4294672.343000] ACPI: setting ELCR to 0800
(from 0e20)
Dec 20 15:48:56 localhost kernel: [4294672.345000] CPU0: AMD Duron(tm) processor
stepping 01
Dec 20 15:48:56 localhost kernel: [4294672.345000] SMP motherboard not detected.
Dec 20 15:48:56 localhost kernel: [4294672.345000] Local APIC not detected.
Using dummy APIC emulation.
Dec 20 15:48:56 localhost kernel: [4294672.345000] Brought up 1 CPUs
Dec 20 15:48:56 localhost kernel: [4294672.346000] NET: Registered protocol
family 16
Dec 20 15:48:56 localhost kernel: [4294672.346000] EISA bus registered
Dec 20 15:48:56 localhost kernel: [4294672.346000] ACPI: bus type pci registered
Dec 20 15:48:56 localhost kernel: [4294672.362000] PCI: PCI BIOS revision 2.10
entry at 0xfb4e0, last bus=1
Dec 20 15:48:56 localhost kernel: [4294672.362000] PCI: Using configuration type 1
Dec 20 15:48:56 localhost kernel: [4294672.363000] ACPI: Subsystem revision 20050916
Dec 20 15:48:56 localhost kernel: [4294672.375000] ACPI: Interpreter enabled
Dec 20 15:48:56 localhost kernel: [4294672.375000] ACPI: Using PIC for interrupt
routing
Dec 20 15:48:56 localhost kernel: [4294672.376000] ACPI: PCI Root Bridge [PCI0]
(0000:00)
Dec 20 15:48:56 localhost kernel: [4294672.376000] PCI: Probing PCI hardware
(bus 00)
Dec 20 15:48:56 localhost kernel: [4294672.376000] ACPI: Assume root bridge
[\_SB_.PCI0] bus is 0
Dec 20 15:48:56 localhost kernel: [4294672.378000] Disabling VIA memory write
queue (PCI ID 0305, rev 02): [55] 89 & 1f -> 09
Dec 20 15:48:56 localhost kernel: [4294672.378000] PCI quirk: region 4000-40ff
claimed by vt82c586 ACPI
Dec 20 15:48:56 localhost kernel: [4294672.378000] PCI quirk: region 6000-607f
claimed by vt82c686 HW-mon
Dec 20 15:48:56 localhost kernel: [4294672.378000] PCI quirk: region 5000-500f
claimed by vt82c686 SMB
Dec 20 15:48:56 localhost kernel: [4294672.379000] Boot video device is 0000:01:00.0
Dec 20 15:48:56 localhost kernel: [4294672.379000] ACPI: PCI Interrupt Routing
Table [\_SB_.PCI0._PRT]
Dec 20 15:48:56 localhost kernel: [4294672.405000] ACPI: PCI Interrupt Link
[LNKA] (IRQs 1 3 4 5 6 7 10 11 12 14 15) *9
Dec 20 15:48:56 localhost kernel: [4294672.405000] ACPI: PCI Interrupt Link
[LNKB] (IRQs 1 3 4 5 6 7 10 *11 12 14 15)
Dec 20 15:48:56 localhost kernel: [4294672.406000] ACPI: PCI Interrupt Link
[LNKC] (IRQs 1 3 4 5 6 7 *10 11 12 14 15)
Dec 20 15:48:56 localhost kernel: [4294672.406000] ACPI: PCI Interrupt Link
[LNKD] (IRQs 1 3 4 *5 6 7 10 11 12 14 15)
Dec 20 15:48:56 localhost kernel: [4294672.410000] Linux Plug and Play Support
v0.97 (c) Adam Belay
Dec 20 15:48:56 localhost kernel: [4294672.410000] pnp: PnP ACPI init
Dec 20 15:48:56 localhost kernel: [4294672.415000] pnp: PnP ACPI: found 12 devices
Dec 20 15:48:56 localhost kernel: [4294672.415000] PnPBIOS: Disabled by ACPI PNP
Dec 20 15:48:56 localhost kernel: [4294672.415000] PCI: Using ACPI for IRQ routing
Dec 20 15:48:56 localhost kernel: [4294672.415000] PCI: If a device doesn't
work, try "pci=routeirq".  If it helps, post a report
Dec 20 15:48:56 localhost kernel: [4294672.446000] PCI: Bridge: 0000:00:01.0
Dec 20 15:48:56 localhost kernel: [4294672.446000]   IO window: disabled.
Dec 20 15:48:56 localhost kernel: [4294672.446000]   MEM window: d8000000-d9ffffff
Dec 20 15:48:56 localhost kernel: [4294672.446000]   PREFETCH window:
d0000000-d7ffffff
Dec 20 15:48:56 localhost kernel: [4294672.446000] PCI: Setting latency timer of
device 0000:00:01.0 to 64
Dec 20 15:48:56 localhost kernel: [4294672.447000] audit: initializing netlink
socket (disabled)
Dec 20 15:48:56 localhost kernel: [4294672.447000] audit(1135093677.445:1):
initialized
Dec 20 15:48:56 localhost kernel: [4294672.447000] VFS: Disk quotas dquot_6.5.1
Dec 20 15:48:56 localhost kernel: [4294672.447000] Dquot-cache hash table
entries: 1024 (order 0, 4096 bytes)
Dec 20 15:48:56 localhost kernel: [4294672.447000] Initializing Cryptographic API
Dec 20 15:48:56 localhost kernel: [4294672.447000] io scheduler noop registered
Dec 20 15:48:56 localhost kernel: [4294672.447000] io scheduler anticipatory
registered
Dec 20 15:48:56 localhost kernel: [4294672.447000] io scheduler deadline registered
Dec 20 15:48:56 localhost kernel: [4294672.447000] io scheduler cfq registered
Dec 20 15:48:56 localhost kernel: [4294672.447000] PCI: Disabling Via external
APIC routing
Dec 20 15:48:56 localhost kernel: [4294672.448000] isapnp: Scanning for PnP cards...
Dec 20 15:48:56 localhost kernel: [4294672.805000] isapnp: No Plug & Play device
found
Dec 20 15:48:56 localhost kernel: [4294672.829000] PNP: PS/2 Controller
[PNP0303:PS2K,PNP0f13:PS2M] at 0x60,0x64 irq 1,12
Dec 20 15:48:56 localhost kernel: [4294672.829000] serio: i8042 AUX port at
0x60,0x64 irq 12
Dec 20 15:48:56 localhost kernel: [4294672.830000] serio: i8042 KBD port at
0x60,0x64 irq 1
Dec 20 15:48:56 localhost kernel: [4294672.830000] Serial: 8250/16550 driver
$Revision: 1.90 $ 4 ports, IRQ sharing enabled
Dec 20 15:48:56 localhost kernel: [4294672.830000] serial8250: ttyS0 at I/O
0x3f8 (irq = 4) is a 16550A
Dec 20 15:48:56 localhost kernel: [4294672.830000] serial8250: ttyS1 at I/O
0x2f8 (irq = 3) is a 16550A
Dec 20 15:48:56 localhost kernel: [4294672.831000] 00:07: ttyS0 at I/O 0x3f8
(irq = 4) is a 16550A
Dec 20 15:48:56 localhost kernel: [4294672.832000] 00:08: ttyS1 at I/O 0x2f8
(irq = 3) is a 16550A
Dec 20 15:48:56 localhost kernel: [4294672.833000] RAMDISK driver initialized:
16 RAM disks of 65536K size 1024 blocksize
Dec 20 15:48:56 localhost kernel: [4294672.833000] Uniform Multi-Platform E-IDE
driver Revision: 7.00alpha2
Dec 20 15:48:56 localhost kernel: [4294672.833000] ide: Assuming 33MHz system
bus speed for PIO modes; override with idebus=xx
Dec 20 15:48:56 localhost kernel: [4294672.833000] ACPI: bus type ide registered
Dec 20 15:48:56 localhost kernel: [4294672.833000] mice: PS/2 mouse device
common for all mice
Dec 20 15:48:56 localhost kernel: [4294672.834000] EISA: Probing bus 0 at eisa.0
Dec 20 15:48:56 localhost kernel: [4294672.834000] Cannot allocate resource for
EISA slot 4
Dec 20 15:48:56 localhost kernel: [4294672.834000] Cannot allocate resource for
EISA slot 5
Dec 20 15:48:56 localhost kernel: [4294672.834000] Cannot allocate resource for
EISA slot 6
Dec 20 15:48:56 localhost kernel: [4294672.834000] EISA: Detected 0 cards.
Dec 20 15:48:56 localhost kernel: [4294672.834000] NET: Registered protocol family 2
Dec 20 15:48:56 localhost kernel: [4294672.844000] IP route cache hash table
entries: 32768 (order: 5, 131072 bytes)
Dec 20 15:48:56 localhost kernel: [4294672.844000] TCP established hash table
entries: 131072 (order: 8, 1572864 bytes)
Dec 20 15:48:56 localhost kernel: [4294672.850000] TCP bind hash table entries:
65536 (order: 7, 786432 bytes)
Dec 20 15:48:56 localhost kernel: [4294672.854000] TCP: Hash tables configured
(established 131072 bind 65536)
Dec 20 15:48:56 localhost kernel: [4294672.854000] TCP reno registered
Dec 20 15:48:56 localhost kernel: [4294672.854000] TCP bic registered
Dec 20 15:48:56 localhost kernel: [4294672.854000] NET: Registered protocol family 1
Dec 20 15:48:56 localhost kernel: [4294672.854000] NET: Registered protocol family 8
Dec 20 15:48:56 localhost kernel: [4294672.854000] NET: Registered protocol
family 20
Dec 20 15:48:56 localhost kernel: [4294672.854000] Using IPI No-Shortcut mode
Dec 20 15:48:56 localhost kernel: [4294672.854000] ACPI wakeup devices: 
Dec 20 15:48:56 localhost kernel: [4294672.854000] SLPB PCI0 USB0 USB1 MODM UAR1
UAR2 
Dec 20 15:48:56 localhost kernel: [4294672.854000] ACPI: (supports S0 S1 S4 S5)
Dec 20 15:48:56 localhost kernel: [4294672.855000] input: AT Translated Set 2
keyboard as /class/input/input0
Dec 20 15:48:56 localhost kernel: [4294672.856000] Freeing unused kernel memory:
316k freed
Dec 20 15:48:56 localhost kernel: [4294672.980000] vga16fb: initializing
Dec 20 15:48:56 localhost kernel: [4294672.980000] vga16fb: mapped to 0xc00a0000
Dec 20 15:48:56 localhost kernel: [4294673.110000] Console: switching to colour
frame buffer device 80x25
Dec 20 15:48:56 localhost kernel: [4294673.110000] fb0: VGA16 VGA frame buffer
device
Dec 20 15:48:56 localhost kernel: [4294674.253000] Capability LSM initialized
Dec 20 15:48:56 localhost kernel: [4294674.328000] ACPI: CPU0 (power states:
C1[C1] C2[C2])
Dec 20 15:48:56 localhost kernel: [4294674.328000] ACPI: Processor [CPU0]
(supports 2 throttling states)
Dec 20 15:48:56 localhost kernel: [4294675.380000] HPT302: IDE controller at PCI
slot 0000:00:0f.0
Dec 20 15:48:56 localhost kernel: [4294675.381000] ACPI: PCI Interrupt Link
[LNKB] enabled at IRQ 11
Dec 20 15:48:56 localhost kernel: [4294675.381000] PCI: setting IRQ 11 as
level-triggered
Dec 20 15:48:56 localhost kernel: [4294675.381000] ACPI: PCI Interrupt
0000:00:0f.0[A] -> Link [LNKB] -> GSI 11 (level, low) -> IRQ 11
Dec 20 15:48:56 localhost kernel: [4294675.381000] HPT302: chipset revision 2
Dec 20 15:48:56 localhost kernel: [4294675.381000] HPT302: 100%% native mode on
irq 11
Dec 20 15:48:56 localhost kernel: [4294675.381000] HPT37X: using 33MHz PCI clock
Dec 20 15:48:56 localhost kernel: [4294675.381000]     ide2: BM-DMA at
0xb800-0xb807, BIOS settings: hde:DMA, hdf:pio
Dec 20 15:48:56 localhost kernel: [4294675.381000] HPT37X: using 33MHz PCI clock
Dec 20 15:48:56 localhost kernel: [4294675.381000]     ide3: BM-DMA at
0xb808-0xb80f, BIOS settings: hdg:pio, hdh:pio
Dec 20 15:48:56 localhost kernel: [4294675.381000] Probing IDE interface ide2...
Dec 20 15:48:56 localhost kernel: [4294675.645000] hde: Maxtor 6B200M0, ATA DISK
drive
Dec 20 15:48:56 localhost kernel: [4294676.258000] ide2 at 0xa800-0xa807,0xac02
on irq 11
Dec 20 15:48:56 localhost kernel: [4294676.258000] Probing IDE interface ide3...
Dec 20 15:48:56 localhost kernel: [4294676.777000] HPT370: IDE controller at PCI
slot 0000:00:13.0
Dec 20 15:48:56 localhost kernel: [4294676.777000] ACPI: PCI Interrupt Link
[LNKC] enabled at IRQ 10
Dec 20 15:48:56 localhost kernel: [4294676.777000] PCI: setting IRQ 10 as
level-triggered
Dec 20 15:48:56 localhost kernel: [4294676.777000] ACPI: PCI Interrupt
0000:00:13.0[A] -> Link [LNKC] -> GSI 10 (level, low) -> IRQ 10
Dec 20 15:48:56 localhost kernel: [4294676.777000] HPT370: chipset revision 3
Dec 20 15:48:56 localhost kernel: [4294676.777000] HPT370: 100%% native mode on
irq 10
Dec 20 15:48:56 localhost kernel: [4294676.777000] HPT37X: using 33MHz PCI clock
Dec 20 15:48:56 localhost kernel: [4294676.777000]     ide4: BM-DMA at
0xcc00-0xcc07, BIOS settings: hdi:pio, hdj:pio
Dec 20 15:48:56 localhost kernel: [4294676.777000] HPT37X: using 33MHz PCI clock
Dec 20 15:48:56 localhost kernel: [4294676.778000]     ide5: BM-DMA at
0xcc08-0xcc0f, BIOS settings: hdk:DMA, hdl:pio
Dec 20 15:48:56 localhost kernel: [4294676.778000] Probing IDE interface ide4...
Dec 20 15:48:56 localhost kernel: [4294677.042000] hdi: Maxtor 4D080H4, ATA DISK
drive
Dec 20 15:48:56 localhost kernel: [4294677.654000] ide4 at 0xbc00-0xbc07,0xc002
on irq 10
Dec 20 15:48:56 localhost kernel: [4294677.654000] Probing IDE interface ide5...
Dec 20 15:48:56 localhost kernel: [4294677.918000] hdk: SAMSUNG SP1604N, ATA
DISK drive
Dec 20 15:48:56 localhost kernel: [4294678.530000] ide5 at 0xc400-0xc407,0xc802
on irq 10
Dec 20 15:48:56 localhost kernel: [4294678.537000] VP_IDE: IDE controller at PCI
slot 0000:00:07.1
Dec 20 15:48:56 localhost kernel: [4294678.537000] PCI: Via IRQ fixup for
0000:00:07.1, from 255 to 0
Dec 20 15:48:56 localhost kernel: [4294678.537000] VP_IDE: chipset revision 16
Dec 20 15:48:56 localhost kernel: [4294678.537000] VP_IDE: not 100%% native
mode: will probe irqs later
Dec 20 15:48:56 localhost kernel: [4294678.537000] VP_IDE: VIA vt82c686a (rev
22) IDE UDMA66 controller on pci0000:00:07.1
Dec 20 15:48:56 localhost kernel: [4294678.537000]     ide0: BM-DMA at
0x9000-0x9007, BIOS settings: hda:DMA, hdb:DMA
Dec 20 15:48:56 localhost kernel: [4294678.537000]     ide1: BM-DMA at
0x9008-0x900f, BIOS settings: hdc:pio, hdd:pio
Dec 20 15:48:56 localhost kernel: [4294678.537000] Probing IDE interface ide0...
Dec 20 15:48:56 localhost kernel: [4294678.563000] hde: max request size: 1024KiB
Dec 20 15:48:56 localhost kernel: [4294678.580000] hde: 398297088 sectors
(203928 MB) w/8192KiB Cache, CHS=24792/255/63, UDMA(33)
Dec 20 15:48:56 localhost kernel: [4294678.581000] hde: cache flushes supported
Dec 20 15:48:56 localhost kernel: [4294678.582000]  hde: hde1 hde2 < hde5 hde6
hde7 hde8 > hde3
Dec 20 15:48:56 localhost kernel: [4294678.623000] hdi: max request size: 128KiB
Dec 20 15:48:56 localhost kernel: [4294678.625000] hdi: 160086528 sectors (81964
MB) w/2048KiB Cache, CHS=65535/16/63, UDMA(100)
Dec 20 15:48:56 localhost kernel: [4294678.625000] hdi: cache flushes not supported
Dec 20 15:48:56 localhost kernel: [4294678.625000]  hdi: hdi1 hdi2 hdi3 < hdi5 >
Dec 20 15:48:56 localhost kernel: [4294678.666000] hdk: max request size: 1024KiB
Dec 20 15:48:56 localhost kernel: [4294678.667000] hdk: 312581808 sectors
(160041 MB) w/2048KiB Cache, CHS=19457/255/63, UDMA(100)
Dec 20 15:48:56 localhost kernel: [4294678.667000] hdk: cache flushes supported
Dec 20 15:48:56 localhost kernel: [4294678.668000]  hdk: hdk1 hdk2 hdk3
Dec 20 15:48:56 localhost kernel: [4294678.681000] ide0: I/O resource
0x3F6-0x3F6 not free.
Dec 20 15:48:56 localhost kernel: [4294678.681000] ide0: ports already in use,
skipping probe
Dec 20 15:48:56 localhost kernel: [4294678.681000] Probing IDE interface ide1...
Dec 20 15:48:56 localhost kernel: [4294679.200000] Probing IDE interface ide3...
Dec 20 15:48:56 localhost kernel: [4294679.331000] hda: ARTEC WRR-4848 1.00,
ATAPI CD/DVD-ROM drive
Dec 20 15:48:56 localhost kernel: [4294679.719000] ide0 at 0x1f0-0x1f7,0x3f6 on
irq 14
Dec 20 15:48:56 localhost kernel: [4294680.046000] hdb: HL-DT-ST DVDRAM
GSA-4160B, ATAPI CD/DVD-ROM drive
Dec 20 15:48:56 localhost kernel: [4294680.098000] register_blkdev: cannot get
major 3 for ide0
Dec 20 15:48:56 localhost kernel: [4294680.098000] ide0: failed to initialize
IDE interface
Dec 20 15:48:56 localhost kernel: [4294680.098000] Probing IDE interface ide1...
Dec 20 15:48:56 localhost kernel: [4294680.635000] hda: ATAPI 48X CD-ROM CD-R/RW
drive, 2048kB Cache, UDMA(33)
Dec 20 15:48:56 localhost kernel: [4294680.635000] Uniform CD-ROM driver
Revision: 3.20
Dec 20 15:48:56 localhost kernel: [4294682.861000] Attempting manual resume
Dec 20 15:48:56 localhost kernel: [4294682.883000] kjournald starting.  Commit
interval 5 seconds
Dec 20 15:48:56 localhost kernel: [4294682.883000] EXT3-fs: mounted filesystem
with ordered data mode.
Dec 20 15:48:56 localhost kernel: [4294684.024000] md: md driver 0.90.3
MAX_MD_DEVS=256, MD_SB_DISKS=27
Dec 20 15:48:56 localhost kernel: [4294684.024000] md: bitmap version 4.39
Dec 20 15:48:56 localhost kernel: [4294686.107000] Adding 1887596k swap on
/dev/hde5.  Priority:-1 extents:1 across:1887596k
Dec 20 15:48:56 localhost kernel: [4294686.526000] EXT3 FS on hde3, internal journal
Dec 20 15:48:56 localhost kernel: [4294691.004000] pci_hotplug: PCI Hot Plug PCI
Core version: 0.5
Dec 20 15:48:56 localhost kernel: [4294691.143000] Linux agpgart interface
v0.101 (c) Dave Jones
Dec 20 15:48:56 localhost kernel: [4294691.147000] agpgart: Detected VIA
Twister-K/KT133x/KM133 chipset
Dec 20 15:48:56 localhost kernel: [4294691.166000] agpgart: AGP aperture is 256M
@ 0xc0000000
Dec 20 15:48:56 localhost kernel: [4294691.478000] shpchp: Standard Hot Plug PCI
Controller Driver version: 0.4
Dec 20 15:48:56 localhost kernel: [4294691.494000] parport_pc: VIA 686A/8231
detected
Dec 20 15:48:56 localhost kernel: [4294691.494000] parport_pc: probing current
configuration
Dec 20 15:48:56 localhost kernel: [4294691.494000] parport_pc: Current parallel
port base: 0x378
Dec 20 15:48:56 localhost kernel: [4294691.494000] parport0: PC-style at 0x378,
irq 7 [PCSPP,TRISTATE,EPP]
Dec 20 15:48:56 localhost kernel: [4294691.518000] Real Time Clock Driver v1.12
Dec 20 15:48:56 localhost kernel: [4294691.528000] input: PC Speaker as
/class/input/input1
Dec 20 15:48:56 localhost kernel: [4294691.559000] r8169 Gigabit Ethernet driver
2.2LK loaded
[...]

Cheers,
   Stefan