A cache file has been corrupted. You can reset the cache file with a simple /Applications/Utilities/Terminal.app and at the first Terminal prompt put in the Terminal code (after you quit all Applications):
Code:
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user
After you let the Terminal program run and know it reset the cache you will know it is finished when you get another Terminal prompt. Then you can close Terminal and the right click for applications will work correctly again. Good Luck.