As always with SCSI: check termination & termpower (JP1)
No need to run HDToolbox or such, just install, setup & mount the CD driver.
I think the problem he expressed was that just running HDToolbox caused a reset.
I recall having a problem similar when I first got my WarpEngine. I believe I resolved it by putting termination on the accelerator. In the end: termination on the accelerator (the beginning of the cable,) TRMPWR from the hard drive, then termination at the end of the cable past the Zip drive. Also, as I believe has been mentioned in other SCSI trouble threads, applying TRMPWR (or TERMPWR) from multiple devices should not hurt anything.