Veritas Backup-Exec.

Currently running Backup-Exec. ver. 8.5 on a Novell server, ver. 5.1 using a Sony Ait-2 tape drive. during tape back-up (about 2 min.’s into it), I receive the following error….”tape backup function terminated by keyboard request. This is a unattended backup run at night. Any ideas as to what might be causing this?????