My Motherboard is Gigabyte GA-P35-DS3R
I have a couple of the DS3x motherboards, one with a Q6600. I had a problem with the stock HS on that one and could never get the temp at load below 70c. I gave up and installed a thermalright ultima 90 and load temps are in the low to mid 40s.
There was nothing obviously wrong with the HS or the MB but every attempt to reseat it did not resolve the problem.