I just made the transition from pc's to macs. I bought three iMac G5's the day they came out, so I've had them around 2-3 months. Here's the problem:

The power cord on one of the computers was accidently pulled out while it was running. The computer began have problems.

The symptoms were:
-It ran much slower than usual.
-It locked up when I tried to reboot it. All of the icons would dissapear, but that was all.
-It wouldn't start up. It would get to the grey screen with the apple symbol, but wouldn't go any further. Eventually, the fans would start racing but it didn't ever do anything.

I thought the power cord accident might be the problem until a second computer started doing the same things. The second computer has had no misuse or accidents to my knowledge. I've tried several things to identify the problem(s). I've tried web searches for similar problems, mac support (they recommended archive and disk repair), and several other things.

I have been very happy with my switch to macs until now. Any help would be great!