A friend of mine who is a bit of a OC genius (not being sarcastic) adjusted it bit by bit. The PC, being watercooled managed to still maintain a nice low temp setting.
Well I just got home from work a few hours ago and first thing I did was wind the clocks multiplier down from 22 to 20 (CPU speed is now at 3.5ghz) and then tried OA, game ran fine, was able to finish the first mission without a hitch and play part of the second one.
Cheers for all input everyone.