[CentOS] USB drive fails at sector 0xFFFFFFF

I'm backing up to a NTFS partition on an external USB drive with dump. I'm 
seeing failures in /var/log/messages reading sector 0xFFFFFFF that cause 
the verify pass to fail. Are there any known problems in the USB driver?

Kernel via uname -a:

Linux segw2.mpa.lan 2.6.18-92.1.6.el5 #1 SMP Wed Jun 25 13:49:24 EDT 2008 
i686 i686 i386 GNU/Linux

Message reported. (Note the number 268435455, which is 0xFFFFFFF, and 
occurs every time I see this happen. But a subsequent attempt to read this 
region with dd succeeds, so it appears to be intermittent, or dependent on 
some other precondition.)

Sep  7 10:48:39 segw2 kernel: sd 5:0:0:0: Device not ready: <6>: Current: 
sense key: Not Ready
Sep  7 10:48:39 segw2 kernel:     Add. Sense: Logical unit not ready, cause 
not reportable
Sep  7 10:48:39 segw2 kernel:
Sep  7 10:48:39 segw2 kernel: end_request: I/O error, dev sdb, sector 
268435455
Sep  7 10:48:39 segw2 kernel: Buffer I/O error on device sdb1, logical 
block 33554424
Sep  7 10:48:39 segw2 kernel: sd 5:0:0:0: Device not ready: <6>: Current: 
sense key: Not Ready
Sep  7 10:48:39 segw2 kernel:     Add. Sense: Logical unit not ready, cause 
not reportable
Sep  7 10:48:39 segw2 kernel:
Sep  7 10:48:39 segw2 kernel: end_request: I/O error, dev sdb, sector 
268435455
Sep  7 10:48:39 segw2 kernel: Buffer I/O error on device sdb1, logical 
block 33554424