My laptop Samsung RF511 is overheating. I noticed this problem while playing minecraft: my computer would suddenly shut down. I checked
/var/log/kern.log and sure enough the system reported temperature was over 90 degrees at the time of shutdown. In order to diagnose the problem I installed Psensor.
I am using Bumblebee. So I thought to try the approach mentioned in this question and ran
optirun glxspheres. No problem! Temperature was a steady 60 across the board. So, with glxgears still running I switched workspaces to my browser in order to pursue another avenue. At that moment Psensor reported temperatures up to 90 degrees! When I switched back to the desktop running glxgears, everything went back to normal.
This fits the previous crashes, since when I play minecraft I spend a lot of time AFK in a different desktop.
I'm using Ubuntu 11.10, kernel 3.0.0-31-generic.