Backup Scan pending

We have a DELL PV132T with LTO3 driver, starting from some weeks ago I have some issue where we need t perform a backup .

When the backup job starts , I see the Backup Scan running and the Symantec Backup Exec shows this message and no further actions are performed.
The strange thing is that some little backup job is performed, i created for these tests backups for different server and folders and some of these works well....
I have also changed the backup hardware but wihtout positive results.

Also I have installed the latest driver pack for 11d (6235), but no changes on this issue...

Any ideas or experience about this issue ?

Thanks