Didn't read much of the replies, but sounds like power supply. My mac went through that... fan burnt out and just kept turning off.

I saw temps for everything else so I assume you weren't taking temps on the supply?

Not quite sure how to take PSU temperatures.. but I replaced the power supply with a friends to check whether it was the power supply, and since I have switched them, it works fine.

So the power supply is/was faulty, using a 420W atm, going to send this one back to overclockers... thanks a lot for your help...

Another problem was I put too much thermal paste on, so contact to and from the CPU and heatsink wasn't properlyfitted.

Yea.. too much paste will do more harm than good.. always keep it really thin.. glad to hear no more shutdowns