I have Vista x64, 4GB RAM, a Q9650 and a GTX295 with the latest driver installed (191.07). Recently I have been noticing shader probles with my card. The shadows seems like grey clouds and flicker when I move about. Here's two photos I made to display the effect, as I had problems producing an ingamer screenshot as the pic would not generate in the appropriate folder.
This is a level in COD4 modern warfare (Ultimatum) where the shader anomaly is particularly obvious. For comparison, here's a Youtube video from some guy playing through the same level, and you will see that the trees look perfectly fine and aren't blurred out by shadows like in my version: