Originally Posted by setishock
Did you spread the paste around on the cpu chip or just set the heatsink down on it(the blob of thermal paste)? If you didn't spread it around you have areas of the cpu not getting cooled. Those parts of the cpu chip are not making contact with the heatsink. We call those hotspots and they're bad news.
I myself don't subscribe to the "spread it around theory", my process involves putting a grain of rice sized blob on the cpu and attaching the heatsink and fan, giving a slight twist of the heatsink to eliminate any possible air bubbles. Because the tolerance between the two faces is so small the pressure of the heatsink being tightened down is sufficient to spread the compound. One thing though, I always ensure the compound is warmish to help with the spread.
Arctic Silver 5 has one of the best instruction sheets I have seen for thermal compound and while it is obviously AS5 specific it is a good general all round guide. As a matter of interest have a look at the dual core instructions, because dual core is an oblong as opposed to the single core square the instructions now state a "thin line" to correspond with the dual cores orientation. (No instructions for quad cores yet but one would assume it's back to a square and a blob)