I have had my white MacBook (2 ghz, 4 gbs ram, x3100, leopard) for over a year and I (stupidly) never bought the Applecare warranty. During my first year I had heating issues and was told my fan sensor was bad. So, they replaced the logic board because the fan was soldered onto it, and reset the cpu onto the new board. Now I believe I'm having heating issues again. While doing nothing but browsing the internet (or even with nothing running at all) my fans will max to 6,000 rpm and according to istat pro, my cpu and airport temps will idle above 70 degree Celsius. They usually stay below 75, but they have gone up to around 77 at times (they rarely hit 80). The heatsink temps stay roughly in the 60s. The bottom of the computer gets scorchingly hot, as does to the right of the trackpad where your right-hand wrist sits. I have often smelled what I think is burning plastic, although the local Apple store told it was not (it didn't smell when they put it through their stress tests last year). Now, here's the weird thing. Sometimes this will happen while the Mac is plugged in, and when I unplug it the temps and fans often cut back almost instantly. So, could this be a charging issue and should I reset the charge cycle? iStat says my battery health is at 98% with 352 cycles. As of writing this, everything is cool and temps are idling right at or below 50 Celsius, except for the airport card, which is at 65. This is the coolest its been in days, and it's even plugged in. I did awake it from being asleep though - could that have correctly set the charging cycle? I have been turning it on and off since this has been happening - I had it in a zipper fabric sleeve a month ago, and when I took it out it was burning hot and the fans were going crazy. I've watched the activity monitor and istat when the temps rise, and nothing is ever higher than 5 - 10%, which makes me think it's a hardware issue. Has anyone had this issue, or know how to fix it? Thanks!