Just a few days ago (this past Tuesday, I think), I started noticing some shadowing glitches when I play Skyrim. Large overcasting shadows would appear and move around as I move the mouse. They happen at night too and in dungeons, making it hard to see. Today, I noticed that I also can no longer see underwater. As soon as I submerge my character, the screen goes gray and can't see anything. I have a dual nVidia 8800GT's set-up with SLI. Prior to Tuesday of this week, I had absolutely no problems with graphic performance. What do I need to do to fix this?