well, it could be the IHS. i mean its got a layer of thermal compound between the cores and the integrated heatsink that sits on top of it.
taking it off is risky though, since the IHS is there to keep the sensitive cores from being damaged... though they used to produce cpu's without IHS's all the time.
what are you using to report temps? because i find that TAT gives readings much higher than speedfan and the bios, which use a sensor on the motherboard. the temperature on the cpu core will be the one taken by TAT since its a program made by intel. as long as its below 60C it shouldn't be in any danger really.
you might try putting the heatsink back on, this time with less thermal compound. the AS5 actually has a thermal conductivity rating of about 9, whereas pure copper has a rating around 80 or so... the more contact with the copper the better, AS5 is only meant to fill in the gaps.
btw AS5 doesnt EVER bond with the cpu... if you run a dual prime95 test and max the temps overnight and then turn the comp off and let it cool to room temperature it excercises the compound though.
basically heat = movement and movement = AS5 fills in the cracks and lets the copper contact with the cpu instead of the compound... then letting it cool to room temp stops the movement and settles the compound.
this "settling" process could take up to 200hrs. (8 and 1/3 full days)