iMac Overheating?

Matt Bacon reports that his flat panel iMac automatically shuts off after performing some processor intensive tasks.

"I have noticed that the machine seems to be getting pretty hot when it starts shutting down -- playing Otto Matic in particular seems to have a strong heating effect."

Bacon reports that pulling the power cord and plugging it back in is the only way to resume power.

Knowledge Base article 95164 (iMac (Flat Panel): Computer Will Not Turn On) offers only cable tightening and device removal as a procedure for eliminating power-on problems.