backup problems with v 8.5 "request could not be performed because....

[AceHigh1234]

The last three days, our backup has failed. We back up the system state data, as well as a network directory (locally hosted) and an accounting program. Veritas logs it as 2 seperate backup sets, one for the system state and one for the rest of the files. The failure of the backup happens in the middle of the verify operatin on set #2 (the non-system state data) every time, giving me the errors below.
This has happened in the past, but went away on it's own after one occurance, only to pop up again later. I am pretty sure it's not the tapes, as they aren't TOO old and we use a different tape each night and it seems strange that they would 'fail' and then work fine for months and then 3 seperate tapes 'fail' all at once. The error messages are shown below, and as always
Thanks in Advance

This is copied out of Backup exec's log
Storage device "SEAGATE 1" reported an error on a request to write data to media.

Error reported:
The request could not be performed because of an I/O device error.

^ ^ ^ ^ ^



And this is the error log from windows 2000 server Event viewer for the exact same time
Event Type: Error
Event Source: ini910u
Event Category: None
Event ID: 9
Date: 5/18/2006
Time: 4:26:33 AM
User: N/A
Computer: ASERVER
Description:
The device, \Device\Scsi\ini910u1, did not respond within the timeout period.
Data:
0000: 0f 00 10 00 01 00 68 00 ......h.
0008: 00 00 00 00 09 00 04 c0 .......À
0010: 01 01 00 50 00 00 00 00 ...P....
0018: 01 00 00 00 00 00 00 00 ........
0020: 00 00 00 00 00 00 00 00 ........
0028: 00 00 00 00 06 00 00 00 ........
0030: 00 00 00 00 07 00 00 00 ........