Well I would say this is the cooler at fault. Have you ever installed those crappy push pins before? If I had to guess it is not making great contact thus your having issues.
Read this and make sure your pins are accurate.
http://forums.anandtech.com/showthread.php?t=2047683 is a way you can try now that wont require you to have the above items.
If you still have issues you might want to try it my way and this has worked every time. What you need is the following.
1. Roll of duck tape
2. Screw Driver (flat head)
3. Remove your motherboard
4. No fear of what your about to do.
What you do is put the motherboards CPU "hole" inside the hole of the tape so that when you push the pin in NOTHING gets in its way...this both gives it strength and it allows the push pin to go all the way down.
Then you take the screwdriver and push down on the push pin till its all the way down....duck tape helps even out the pressure as well to avoid damaging your board but I warn you it will still bend a little because it takes a lot of effort to get those things in properly.
I find doing it inside your case the board will "bend" till it hits the tray so you wont get it all the way in correctly thus have gaps and thus cause horrible temps.
Most over heating issues with stock cooling with those are failure to get the pins all the way in correctly. I have the same issue when I first went to the new 775 socket with my Q6600...dropped my temps 20c because it was improperly put in.