Tru64 backup error

Running Tru64 and the library is MSL6000. Also, running Sybase.

Performing tape library inventory.
No values returned by robot list command.
ERROR: Unable to perform preliminary inventory. Job aborting.
Wed May 13 07:00:08 2009: DB_tape_backup process completed.

I'm getting this error on one of our servers. Can someone provide some information on this error?

Thanks,