Expose and keyboard shortcuts stop working

[techmonkey]

This has happen (2) times since I bought my MBP. The only way I can get Expose to work again is to open up the System Preferences and change one of the Expose corners to something else, then change it back to what I had it at. After I do this, all of my corners work correctly. My next issue are the default keyboard shortcuts, specifically F11 and F12. These stop working also. I tried changing them like I did with the Expose corners, but this doesnt work.

Any ideas what may be doing this?