Sort of related to heat... the heatsinks your using..

We had a problem from the vendor we get our boxes from awhile back. They were putting Intel fans on AMD chips.. The tolerance is different between the two types of heatsinks and therefore, the Intel heatsinks were crushing the die on the AMD chips..

Try visually inspecting your chips that you have had problems with, you may have the wrong type of heatsink (for Intel not AMD).