OK I was mistaken when i said it was working fine on the PC. Turns out I must have been plugging it into the 68-pin connection on the card (what is it with Apple only using 50-pin cards) as it's not showing up in the card utility when I use the 50-pin connection/adapter but does when going straight to the 68-pin. Must be a termination issue. So I'll go off and do some reading up on that.

In the meantime, I discovered on xlr8yourmac that it might be possible to flash a Mac bios onto the SCSI card I have in the PC (AHA-2940UW). Only thing is, I'd lose my only working PC SCSI card so I'm not keen on doing that just yet. Especially when I have 3 Mac ones already.