try going into My docs/my games/Dirt2/hardware settings and delete the hardware settings folder. Re-run the game and setup the settings again.
When I set AA to 16XCSAA (I think) the screen stopped refreshing and I had a similar issue. It was either 16 or 8x I can't remember but one of the AA modes causes the game not work right. I deleted the hardware settings stored there and restarted it.
On the GFWL issue, have you tried to remove and install the 3.3 client? This was released just recently...
WeReWoLf - if it were the drivers it would affect every game.