Figured out how to run the file verification, but it didn't work for me. For those like me who are unfamiliar with Steam here's the procedure: 1. Go to Steam 2. Click on View 3. Click on Small Mode 4. Find Skyrim and right click on it 5. Click on Properties 6. Select the tab "Local Files" 7. Click on Verify integrity of game cache This didn't work for me, but I did find a work around by downloading and installing a lighting mod with the mod manager. I suspect that this isn't a common problem, but can occur if you heavily modify Skyrim or have a corrupt game file.