How much mhash/sec are you getting?
Well I'm kinda new to this so maybe my numbers are off. The Diablo miner says I'm getting 80,000-100,000 which I guess is 80-100 mhash/sec. My deepbit mining account says I'm averaging 35-45 though which I think is typically low but about where OSX normally is.
You should be getting way more. I get 110 mhash with a 6750M. Try using poclbm in Windows if you can. Oh and pool sites will never show your actual hashrate. They can't calculate that accurately.