I have a new, week 7, 27" iMac with 2.8 quad core CPU. Activity Monitor shows the "% idle" number jumping anywhere from 49% to 99% (but usually stays around 49%), when I'm actually 99% idle. The "% user" and "% system" numbers are less than 1% when the computer is idle. They just don't add up to 100%. Does anyone else see this? The left top of the computer is hotter than any computer I have had before. This is the third computer that Apple has sent with this problem. Apple Care just says to send it back. Any ideas?