Have you tried deleting it from BackupExec, then deleteing rom device manager, loading the MFG drivers and then re-running the BackupExec Hardware wizard amd telling it to use the installed drivers rather than load Veritas Drivers?
If you shut down all BackupExec services, does NTBackup see it properly?
(FWIW, http://seer.support.veritas.com/docs/271383.htm says that this is a Tested Library)