Intel E8500 rising temp + panic! Thoughts?

Advice appreciated!

I've just inserted an E8500 into my system to replace my E6600. Now Ive done some googling and I understand my replacement Wolfdale will run hotter than my Conroe but it seems to be running way to hot! Either that or CoreTemp is telling porkies.

Now I'm not interested in overclocing at this stage because I've only got a stock cooler, I've cleaned the processor and heatsink with Arcticlean remover and purifier and used Arctic Silver 5. I googled the crap out of how to apply it correctly so I'm confident I have, also confident the heatsink is on properly.

(These temps are according to coretemp).... Now the E6600 was running at idle at about 30-33 degrees and I seen it hitting roughy 60 degrees under load. Now I was happy with that after some research and using the stock cooler.

The E8500 on the other hand is sitting currently at 42 - 45 degrees as I'm typing this only with one browser tab open, just doing the Windows 7 experience index test pushed the coretemp to 99 degrees!!

Now is coretemp telling porkies or have I got a problem? The temps under any load appear to fluctuate wildly.

I would like to point out that this processor was sourced from ebay second hand...