Which HD is that? Cyberstorm SCSI has problems with some makes. I remember that 50 pin IBM drives worked fine but when I tried some wide (68 pin) ones they failed (especially LVD even though they were supposed to have a fallback mode). What helps sometimes is to force the LVD drive into SE mode with a jumper (if it has it). Which HDToolBox do you use? Sometimes I had better luck with the one from 3.1. Also how is your termination?