I have the same problem at two sites.
Site one = new HP server, new HP DAT 72 tape drive, new HP DAT 72 tapes. I am able to back up to the tapes using the Microsoft SBS 2003 Backup but Veritas will not recognise the tapes.
Site two = three year old HP server, three year old HP tape drive, relatively new HP (compatible) tapes. Veritas was backing up quite happily for two weeks or so, now it will not recognise the tapes. There are some tapes listed in the only media set, these are also listed in the offline tapes section.
I will be grateful if anyone can tell me where I am going wrong here! Thank you.