I have a Core 2 Duo and I have made a guide: http://imbacore.blogspot.com/2011/10/how-to-solve-rage-texture-streaming-pop.html See if that helps.
Well you probably have a Nvidia card right? Well i tried everything from there ... Nothing works for me , no matter what i do game always freezes up after intro if Catalyst AI is on , And if its off then its blocky textures time .. Only thing that actually made a difference.. Was going back to 11.9 Drivers , While i still freezed if AI is on , Putting it off made the game not freeze and no more blocky textures , But just like the 11.6 drivers , I was getting 20FPs .. i get 45-60 with the newest driver from ATI so i dont think its a specs problem.
EDIT: - If you have an AMD graphics card with a dual core CPU system you may experience severe hitching and low frame rates.
Since you are on Nvidia , I think you have another problem than what i have , I think you just have texture pop-ins , I get blocky black empty textures .. Like this : http://www.youtube.com/watch?v=z-yl6pDFgtw