Having problems OC'ing this card. It's stock is 600mhz core clock and its factory OC'd to 625mhz which is a minor improvement. However when i try and OC this card using either nTune or RivaTuner it runs "seemingly" fine for about 2 mins then crashes. Crashes in 3Dmark testing aswell. Just generally woundering if any1 can give any advice or want to share their OC'ing experiences with this card.