Extreme heating while closed in backpack

Question

I'm running the most recent iteration of the MacBook 15" - 2.4GHz that I have had for nearly three weeks now. Twice in the last week I have pulled the laptop out of my backpack to find it very hot, so much so that the colors on the LCD were not displaying correctly (no color, just shades of gray) and the battery life was down to about 5%. I shut the computer completely down and let it cool off for an hour or two before turning it back on. When it came back on the LCD worked just fine and the battery charged up to 100% just fine again.
In both cases, the laptop had been plugged in just prior to its being closed and put in the backpack and was at (or very near) 100% battery. The laptop was in the backpack both times for only about an hour. The lid of the laptop had been closed, but the computer had not been manually shut down.
At first I was worried that I had placed the laptop in front of one of my car's heating vents on the way home to create the heat, but the second time that it happened the laptop's bag was sitting in the seat with no vents directly on or near it. Has anyone else experienced this kind of "exceptional" heating while their MBPs are sitting in backpacks/bags? I've just installed the iStat widget so that I can provide more accurate temperature numbers if/when it happens again.
-b-

Answer 1

It would seem that the Mac is waking up or hadn't gone to sleep in the first place.
A little bit of detective work analyzing the system logs can be used to determine if this is the case. If you've never delved into what the logs contain, try this procedure. First put the Mac to sleep, making sure it is really sleeping (pulsing LED pilot light, no sounds from the HDD). Wake it up and open Console, found in Utilities. Examine the contents of the Console Messages window, as well as the system.log output: correlate the time stamps to the various messages the computer puts out as it goes thru the process of going to sleep as well as waking up afterwards. Once familiar with what kind of messages both events (sleep/wakeup) produce, go back in time in the logs to those occasions when you have had the overheating incidents. While the Console Messages output may be truncated, you can usually find older system.log files archived further down the list (i.e., system.log.0.bz2, system.log.1.bz2, etc.). Check and see if the computer is, indeed, waking up when it shouldn't, and the info on the logs is the most reliable way to find out what's going on.
Why? I have the suspicion that the magnetic closure on the new models is not working correctly and that the lid is popping open inside the bags due to a bump or jarring motion. Yours is but the latest of a ever-growing list of similar reports. On previous models you had to push a recessed button to get the lid to open.