Yes i believe it is a heat issue.....
They are petium III processors.
one has the standard factory heatsink, and the other has an antec heatsink.
Standard heatsink CPU- low is 88F high is close to 110F and maybe hotter
antec Heat sink - low is 82F high is close to 98F but not much hotter
i believe while playing Dungeon siege the one cpu gets closer to 115F give or take a little. I haven't been able to test more. When i got these numbers it was after i changed to flow of a rear fan from out to in. which could have fixed this problem but like i said more testing is needed.