My Phenom 9950 started giving me overtemperature (60C) warnings yesterday (from BIOS - couldn't find the temps through Linux because lmsensors was being buggy). I think it's a combination of the rising temperatures (I built & tested the rig when it was freezing in the room) and maybe dust buildup. So what I did - I hit it with canned air and raised the limit before the BIOS starts beeping! No more warnings
If that rig fries, I plan to use a bit of my research assistant money and get myself a heavy-hitter.