usb hard drive changes from /dev/sda to /dev/sdb with sarge

[Jason Dunsmore <jason.public@gmail.com>]

once in a while (can be every couple days or every couple weeks), my
usb hard drive changes from /dev/sda to /dev/sdb, and i see this in
dmesg:


scsi11 (0:0): rejecting I/O to dead device
ReiserFS: sda1: warning: zam-7001: io error in reiserfs_find_entry
scsi11 (0:0): rejecting I/O to dead device
scsi11 (0:0): rejecting I/O to dead device
ReiserFS: sda1: warning: vs-13050: reiserfs_update_sd: i/o failure
occurred tryi
ng to update [1 2 0x0 SD] stat data
scsi11 (0:0): rejecting I/O to dead device
Buffer I/O error on device sda1, logical block 8210
lost page write due to I/O error on sda1
ReiserFS: sda1: warning: journal-837: IO error during journal replay
REISERFS: abort (device sda1): Write error while updating journal
header in flus
h_journal_list
REISERFS: Aborting journal for filesystem on sda1
scsi11 (0:0): rejecting I/O to dead device
Buffer I/O error on device sda1, logical block 2480
lost page write due to I/O error on sda1
Buffer I/O error on device sda1, logical block 2481
lost page write due to I/O error on sda1
scsi11 (0:0): rejecting I/O to dead device
Buffer I/O error on device sda1, logical block 2482
lost page write due to I/O error on sda1
scsi11 (0:0): rejecting I/O to dead device
scsi11 (0:0): rejecting I/O to dead device
ReiserFS: sda1: warning: zam-7001: io error in reiserfs_find_entry
scsi11 (0:0): rejecting I/O to dead device
ReiserFS: sda1: warning: zam-7001: io error in reiserfs_find_entry
scsi11 (0:0): rejecting I/O to dead device
ReiserFS: sdb1: found reiserfs format "3.6" with standard journal
ReiserFS: sdb1: using ordered data mode
ReiserFS: sdb1: journal params: device sdb1, size 8192, journal first
block 18, max trans len 1024, max batch 900, max commit age 30, max
trans age 30
ReiserFS: sdb1: checking transaction log (sdb1)
ReiserFS: sdb1: replayed 3 transactions in 0 seconds
ReiserFS: sdb1: Using r5 hash to sort names


after that happens, i have to remount my usb hard drive under /dev/sdb.
 after a reboot, it's at /dev/sda again. this causes all kinds of
problems, because i back up to that drive, so if it changes and i don't
catch it, my root drive gets maxed out. i'm using the prebuilt
2.6.8-2-k7 kernel with sarge.

any ideas how i can fix this?