I have the same problem, it's also related to Athlon chips design. Athlon chips are good but behave like a stove. Anyway, I found a solution, not too stylish, but it works. Just open the case, and point a fan to the micro (a fan like the ones you use in summer ;) ) That keeps my Athlon 2.4 at 47C +- under 100 % loads for hours.