I have a CSMkIII in my A4000T. No problems here. At one time my system would GURU once on every cold boot and then reboot fine. I think I solved that by adjusting the settings of the Cyberstorm's SCSI controller (in the end I completely disabled the A4000T's built-in SCSI controller as I wasn't using it anyway and having it on slowed boot times. Is your hard drive on the CS's SCSI, the A4000T's SCSI, or the A4000T's IDE? Try disabling the ones you're not using and see if that helps.
There's also some ROM settings in the CS's BIOS menu. I think there may be a rom2fast type setting in there (but I'm not sure). Anyway, try playing around with those settings and see if you get any better luck.