backup fails--bus free state

[Scott Engstrom]

I have a windows2003 server with 2G RAM, RAID1 on onboard adaptec AIC7901 controller, quantum DLT1 VS80 tape drive on a PCI adaptec 3950U2B controller. Novanet backup fails at about 30-32G of 34G data with event viewer error "device\scsi\aic78u21 did not respond within the timeout period" and Novanet error "SCSI bus has unexpectedly gone to a bus free state". I have replaced the scsi cabling, the controller(tried an adaptec 29160 as well), the motherboard, the RAM, the tape drive 3 times. I have called Novanet, Adaptec, and Quantum. I have set the settings in the BIOS to what adaptec recommended. I have updated and reinstalled drivers for the drive and controller.(The backup had gone for 6 months without this problem.) Not sure what to do or where to turn. Would it be worth putting the pagefile on a separate drive, or would this have no impact on the scsi bus problem I appear to be having. Any ideas would be helpful.