FAT partition on usb hdd won't mount

I have a usb hdd, with the partitions:
sdb: sdb1 < sdb5 sdb6 > sdb2

sdb5 is an ext3 parition called "blackie-linux"
sdb6 is a FAT partion, with the name "WINDOWS"
sdb2 is a bpootable FAT partition, called "boot"

when I plug it in to Kubuntu hardy, sdb5 and sdb6 both mount correctly, but sdb2 doesn't mount, with this error message:
"mount: wrong fs type, bad option, bad superblock on /dev/sdb2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so"

sdb2 correctly mounts on my girfriend's gutsy install, as it did when I had gutsy. It's not hugely problematic - there's nothing on there that I need, but it's annoying.

dmesg shows:
[ 2662.632971] usb 2-2: USB disconnect, address 4
[ 2666.152263] usb 5-4: new high speed USB device using ehci_hcd and address 4
[ 2666.221116] usb 5-4: configuration #1 chosen from 1 choice
[ 2666.684213] usbcore: registered new interface driver libusual
[ 2666.906822] Initializing USB Mass Storage driver...
[ 2666.912618] scsi2 : SCSI emulation for USB Mass Storage devices
[ 2666.922603] usbcore: registered new interface driver usb-storage
[ 2666.925161] USB Mass Storage support registered.
[ 2666.927603] usb-storage: device found at 4
[ 2666.929400] usb-storage: waiting for device to settle before scanning
[ 2668.046885] usb-storage: device scan complete
[ 2668.060536] scsi 2:0:0:0: Direct-Access SAMSUNG HM120JC 0000 PQ: 0 ANSI: 0
[ 2668.064683] sd 2:0:0:0: [sdb] 234441648 512-byte hardware sectors (120034 MB)
[ 2668.066682] sd 2:0:0:0: [sdb] Write Protect is off
[ 2668.066700] sd 2:0:0:0: [sdb] Mode Sense: 27 00 00 00
[ 2668.066711] sd 2:0:0:0: [sdb] Assuming drive cache: write through
[ 2668.069138] sd 2:0:0:0: [sdb] 234441648 512-byte hardware sectors (120034 MB)
[ 2668.071124] sd 2:0:0:0: [sdb] Write Protect is off
[ 2668.071138] sd 2:0:0:0: [sdb] Mode Sense: 27 00 00 00
[ 2668.071147] sd 2:0:0:0: [sdb] Assuming drive cache: write through
[ 2668.071164] sdb: sdb1 < sdb5 sdb6 > sdb2
[ 2668.755515] sd 2:0:0:0: [sdb] Attached SCSI disk
[ 2668.755671] sd 2:0:0:0: Attached scsi generic sg1 type 0
[ 2676.306173] b43-phy0 ERROR: PHY transmission error
[ 2684.782836] UDF-fs: No partition found (1)
[ 2685.343487] ISOFS: Unable to identify CD-ROM format.
[ 2685.456440] UDF-fs: No partition found (1)
[ 2685.565253] ISOFS: Unable to identify CD-ROM format.
[ 2686.535285] kjournald starting. Commit interval 5 seconds
[ 2686.536117] EXT3-fs warning: mounting unchecked fs, running e2fsck is recommended
[ 2686.537630] EXT3 FS on sdb5, internal journal
[ 2686.537647] EXT3-fs: mounted filesystem with ordered data mode.

$ uname -a:
Linux naught101-laptop 2.6.24-14-rt #1 SMP PREEMPT RT Wed Apr 2 05:29:15 UTC 2008 i686 GNU/Linux
(this was happening before I was using an RT kernel, I think)

$ lsb_release -rd
Description: Ubuntu hardy (development branch)
Release: 8.04