I think I'm having the same problem.
I don't know much about the advanced or debug menus but from reading around I did follow common steps to try and alleviate it- like disabling HTTP textures and clearing my cache.
I've also tried two graphics cards (most recent drivers), nVidia 9800gt and 250gts with the same results for each.
I too am running Windows 7 64bit though (pro). I hadn't seen anyone else using it except in this thread so it struck me as maybe being a meaningful coincidence.
My processor is an i5 2500k. So... plus one from me as well. ^^