B2D failure to backup Exchange 2003 sp2

Hi folks, I'm getting random failures when backing up Exchange 2003 sp2 to disk. It's failing on at least 50% of the jobs but works perfectly if I backup to tape (Ultrium 3). The final error code is: 0xe00084af "The directory or file was not found, or could not be accessed". In the error pane; "Database was not found, or could not be accessed".

Operating system: Windows 2003 r2

BackupExec v12.5

I've made sure that no other jobs are running at the same time.

Any idea what the problem might be ??

Many thanks