Problems with External USB Hard Drive

[Allen Winter]

Howdy,

I just got a new 160GB external USB Hard drive from Maxtor (the "One Touch").
At first it seemed to work for me without any trouble.  I copied 10GB or so onto it and things look ok.
But a few hours later the drive was unmounted.
There is one big Linux partition with an ext3 filesystem on the drive.  The drive is plugged into a 4-port
Kensington USB hub.

The first sign of trouble I see are these messages from /var/log/messages:
Sep 20 20:01:06 kernel: updfstab: Using deprecated /dev/sg mechanism instead of SG_IO on the actual device
Sep 20 20:01:06 kernel: kudzu: Using deprecated /dev/sg mechanism insteadof SG_IO on the actual device

Later, these messages show up in /var/log/messages when the drive unmounts:
Sep 20 22:02:30  kernel: usb 1-1.2: USB disconnect, address 4
Sep 20 22:09:04 kernel: scsi0 (0:0): rejecting I/O to dead device
Sep 20 22:09:04  kernel: EXT3-fs error (device sda1): ext3_find_entry: reading directory #2 offset 0
Sep 20 22:09:04 kernel: Aborting journal on device sda1.
Sep 20 22:09:04 kernel: scsi0 (0:0): rejecting I/O to dead device
Sep 20 22:09:04 kernel: Buffer I/O error on device sda1, logical block 530
Sep 20 22:09:04 kernel: lost page write due to I/O error on sda1
Sep 20 22:09:04 kernel: scsi0 (0:0): rejecting I/O to dead device
Sep 20 22:09:04 kernel: Buffer I/O error on device sda1, logical block 0
Sep 20 22:09:04 kernel: lost page write due to I/O error on sda1
Sep 20 22:10:08 kernel: scsi0 (0:0): rejecting I/O to dead device
Sep 20 22:10:08 kernel: EXT3-fs error (device sda1): ext3_find_entry: reading directory #2 offset 0
Sep 20 22:10:08 kernel: scsi0 (0:0): rejecting I/O to dead device
Sep 20 22:10:08 kernel: Buffer I/O error on device sda1, logical block 0
Sep 20 22:10:08 kernel: lost page write due to I/O error on sda1
Sep 20 22:10:08 kernel: ext3_abort called.
Sep 20 22:10:08 kernel: EXT3-fs abort (device sda1): ext3_journal_start: Detected aborted journal

Any idea how I can fix this?  After a reboot the drive works again for a little while before unmounting.
I have an FC2 system running the stock 2.6.8-1.521 kernel.

Help! Appreciated,
Allen