The iMac G5 in my signature has been acting up today. It has slipped into a "coma" twice while it was running unattended. Both times, I walked into the room to find the screen blank and the "sleep light" off, but with the internal fans running at full speed (very noisy). Clicking and pressing keyboard keys had no effect. The first time, I unplugged the computer and plugged it back in. It refused to turn on. At one time, it turned on and then immediately turned off, cutting off the startup noise. And then... it worked! I backed up all important files, but no problems emerged, so I assumed it was just a one-time weirdness. Then I walked in to the room later on and it was back it its strange coma state again. This time, I unplugged it and it worked the first time I tried to restart it. I remember reading about a transistor problem that plagued some rev. A iMacs. Also, my iMac's serial number qualifies for this repair extension: http://www.apple.com/support/imac/repairextensionprogram/ What should I do?