dell optiplex gx 270 invisible boot

On a dell GX 270 (a very common 2-3 years old workstation), during all the boot, you don't see anything (black screen) until the graphical interface load (and then it's ok).

Festy Fawn Alpha 4 and then up to date, with this bug all the time (was not in 6.10)

leo@leopc:~$ uname -a
Linux leopc 2.6.20-8-generic #2 SMP Tue Feb 13 05:18:42 UTC 2007 i686 GNU/Linux

leo@leopc:~$ lspci
00:00.0 Host bridge: Intel Corporation 82865G/PE/P DRAM Controller/Host-Hub Interface (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 82865G Integrated Graphics Controller (rev 02)
00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #3 (rev 02)
00:1d.3 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #4 (rev 02)
00:1d.7 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev c2)
00:1f.0 ISA bridge: Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge (rev 02)
00:1f.1 IDE interface: Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller (rev 02)
00:1f.2 IDE interface: Intel Corporation 82801EB (ICH5) SATA Controller (rev 02)
00:1f.3 SMBus: Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus Controller (rev 02)
00:1f.5 Multimedia audio controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) AC'97 Audio Controller (rev 02)
01:0c.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet Controller (rev 02)

ProblemType: Bug
Date: Mon Feb 26 16:27:01 2007
DistroRelease: Ubuntu 7.04
Uname: Linux leopc 2.6.20-8-generic #2 SMP Tue Feb 13 05:18:42 UTC 2007 i686 GNU/Linux