Hello,
Generally, these error messages may occur due to SCSI BUS related issues, which in turn can cause the tape device to work incorrectly.
As a preliminary step to isolate this issue, please try to perform a test backup using "NTbackup" the native backup utility, stopping all Backup Exec services. Please check if the backup works correctly. Do let us know the results. The following technote is useful to resolve the SCSI BUS related issues:
URL - http://seer.support.veritas.com/docs/191158.htm
Regards,
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