hi, have just moved house and plugged in my g5 and it doesnt power up, all that happens is the fans turn a slight bit, and it clicks once. I've tried turning the switch off and on, holding button etc but i think is a more complex solution.
Apple recognizes a problem with G5's where the power supply gives out prematurely. They should replace the power supply if it turns out to be the PS which is the problem. I'd call AppleCare and describe the problem or lug it into a Mac repair shop (my personal last resort) in order to get the official word on it.