Thanks chaps, I'm going to work from the bottom up. I'll swap the power cord on two machines first. I don't think it's overheating, as I can hear the fans whirring (noisy bastards!), but I could use one of those apps that shows you the MB temperature and conditions?!
If it's the power supply, then I have a spare one, but the current one is threaded into the chassis like a work of art. Rather than unweave the rainbow of cables, I'd have to dangle the new box outside the case for a couple of days. If the MB is faulty, then it's game over man! My iMac is now 10 months old now and it hasn't even hiccupped and it's as silent as a cold brick. *GK*
