Are you overclokcing? Overclocking produces more heat.
If not, it sounds like your thermal barrier. Are you both using the same thermal paste?
Did you know that for a new install with thermal paste your temps will start out high and go down after a couple of weeks as the paste stabilises?
how did you install the paste? Thick layers are much worse than slight smear. Also, see the Arctic Silver website for a good description on how to do it right for C2D.