Every once in awhile, Mac OS X seems to lose it’s way with regard to the apps it shows when you right click on a file, and choose “Open With.” For some reason, this is particularly pronounced in Mountain Lion (Apple’s buggiest OS to date).
Here’s how to fix the problem:
Open Terminal.app and issue the following command, which causes Launch Services to rebuild its index.
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user
You may need to restart Finder or reboot to notice the changes.