NT Backup problem in SBServer 4.5

I have SBServer 4,5 and I used NT Backup programe .Now I have problem with the backup ,when I want to excut backup I got notification :A tape device has been detected,and the tape driver started.However ,the tap device is not responding,check that tape device power is on and cables are properly connected.In spite of that alle cables are good, Any idea a bout this problem.