gtx 570 issue

My latest upgrade to a MSI GTX 570 Twin Frozer II,gave me some problems.
It crashes randomly while playing COD Ghosts on high settings and its not due to high temperatures,had a look at the monitoring log and it crashes while at 70C.
Managed to stress out the card,with MSI Combustor and ran the test for 15 and more minutes,hitting even 77-78C.Tried to play the game with an altered core voltage of 1038mV (stock is 988mV),no luck.Screen freezes on last frame,dots and little dizzy stars appear,OS crashes,
Could you help me figure out,what (if) i am doing wrong?

78C is quite a lot of temperature. As I see it has a cooler. It shouldn't be reaching that high temperatures as I know. But it crashes every time it reaches about 65-75C or crashes at random temperatures?

It has reached even 83C without crashing and you can get those temps real easy,I am living in Greece and its already 30C here and its almost 20.30,evening that is!
It crashes at about 70,according to the log provided by Afterburner,doesnt look like a temp issue.

Uninstalled and totally deleted drivers under safe mode,reinstalled latest and things look sorted out.Managed to play on "high" settings,even with 2xMSAA on,the game responded smooth.Hopefully issue solved,i 'll keep the thread open for a couple of days for any input.