Hi,
.
I am having this problem myself and I think I read something about it either here or somewhere else, about someone that fixed his drive using knoppix + parted
.
Here is the diagnostics I could get from my drive, which seemed to be working fine last time I used it and it is not sounded weird or anything like that, so it does not apear to have a physical problem
.
// __
sh-3.00# whoami
root
.
// __
sh-3.00# dmesg | tail
Vendor: A T R 6 Model: 080 4 Rev:
Type: Direct-Access ANSI SCSI revision: 06
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi3, channel 0, id 0, lun 0
.
// __
sh-3.00# mount -t vfat /dev/sda /mnt/sda -r
mount: wrong fs type, bad option, bad superblock on /dev/sda,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

sh-3.00# dmesg | tail
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi3, channel 0, id 0, lun 0
FAT: invalid media value (0x3
VFS: Can't find a valid FAT filesystem on dev sda.
.
// __
sh-3.00# fdisk -l /dev/sda

Disk /dev/sda: 80.0 GB, 80028893184 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sda doesn't contain a valid partition table
.
// __
sh-3.00# dmesg | grep -i sda
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
VFS: Can't find a valid FAT filesystem on dev sda.
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi1, channel 0, id 0, lun 0
VFS: Can't find a valid FAT filesystem on dev sda.
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi2, channel 0, id 0, lun 0
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi3, channel 0, id 0, lun 0
VFS: Can't find a valid FAT filesystem on dev sda.
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
SCSI device sda: 156306432 512-byte hdwr sectors (80029 MB)
sda: asking for cache data failed
sda: assuming drive cache: write through
sda: unknown partition table
Attached scsi disk sda at scsi4, channel 0, id 0, lun 0
.
// __
sh-3.00# fdisk -l

Disk /dev/hda: 13.5 GB, 13578485760 bytes
16 heads, 63 sectors/track, 26310 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes

Device Boot Start End Blocks Id System
/dev/hda1 * 1 12190 6143728+ c W95 FAT32 (LBA)
/dev/hda2 12191 18191 3024504 83 Linux
/dev/hda3 18192 26310 4091976 83 Linux

Disk /dev/sda: 80.0 GB, 80028893184 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sda doesn't contain a valid partition table
.
// __
sh-3.00# parted /dev/sda
GNU Parted 1.6.9
Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
This program is free software, covered by the GNU General Public License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.

Using /UNIONFS/dev/sda
Error: Unable to open /UNIONFS/dev/sda - unrecognised disk label.
Information: The operating system thinks the geometry on /UNIONFS/dev/sda is
9729/255/63. Therefore, cylinder 1024 ends at 8032.499M.
(parted) check
Error: Unable to open /UNIONFS/dev/sda - unrecognised disk label.
(parted) p
Error: Unable to open /UNIONFS/dev/sda - unrecognised disk label.
(parted) q
Information: Don't forget to update /etc/fstab, if necessary.
// __