Comment 46 for bug 563156

Similar to the OP, I was running karmic (updated from Hardy, not scratch install) w/o any power or temp issues; however upon update to lucid (release version), I began to experience periodic overheating on my lenovo thinkpad t400 (automatic, immediate shutdown). At idle, with no applications running, the temperature was consistently ~75-80 Celsius. As this is a dual boot machine with Vista, I benchmarked the temperature under Vista (using Everest) and found it was ~50 degrees Celsius under Vista.

My laptop does *not* have an ATI graphics chip installed (it is available to lenovo's, but mine uses a built-in intel chip).

Based on suggestions found in this thread, http://ubuntuforums.org/showthread.php?t=1454328, I first removed the battery, which reduced the average cpu temperature from 75-80 to 65-75 degrees Celsius.

Next, I updated the bios to the latest release (3.16). However, this had little effect upon the temperature under lucid.

Finally, I modified the BIOS power management settings, so that under BIOS->config->power options

Adaptive Thermal management
Scheme for AC [Maximize Performance]
Scheme for Battery [Balanced]

the 'Scheme for AC' was changed to [Balanced]. Since then, the laptop has returned to a cooler running temperature of 48-53 degrees Celsius.

When I get a chance, I'll buy a can of air to clean the fan out. Still, it isn't clear to me why the temperature under Vista would be cooler prior to making this change to the BIOS, but it's workaround at the least, and hopefully, this info can/will shed some light for the developers.