132T, Backup Exec 9.1, and I/O errors

I have a PowerVault 132T hooked up to a Poweredge 2650 through an Adaptec 7880 SCSI card.  When I run backup jobs, ever job fails with the following message:

Storage device "DELL PV-132T" reported an error on a request to write to data media.

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

I have checked the even log and see no errors.  I have updated both the SCSI card drivers and firmware.  I have also tried running jobs with the Removable Storage service both on and off with no luck.  My usual backup job is about 98 GB and it usually fails after backing up about 20 GB.  I do get a message on server startup that says autoconfiguration for changer 0 failed.  Any help would be appreciated.