Yep...of course, it could have been a faulty cable (although it was brand new). What happened, was I attached it, like you do...and BAM! The BIOS didn't recognise either drive, and one of the drives at least was behaving rather strangely - could eject the tray, but not get it back in (had to push it in manually).
Popped the old cable back on, everything was fine. I did also notice, that on the mobo itself, the Primary IDE was coloured Blue, as is usual for ATA66 etc, but the Secondary IDE on the mobo was just regular Black.
I can always try another cable, though