SCSI nightmare

I have a workgroup server 8550/200. Attached there are a SCSI CD-RW Drive and a Tape Drive. We recently had problems with the tape drive and got a replacement. Since then I have not been able to hook either device up to the server. If i do the server will start but the mouse is frozen. Once I managed to get the tape drive attached but when i later tried both it froze again. Any thoughts.
PS yes its termintated and yes i shut it down first