When a user right clicks a file and selects ‘Open With’ there are multiple copies of the same App listed several times.
This can be fixed by reseting ‘Launch Services’, a set of several files which deals with associating file types with applications. The following instructions will rebuild ‘Launch Services’ for Snow Leopard (10.6), Lion (10.7) and Mountain Lion (10.8)
1. Open Terminal (Available in Finder > Applications > Utilities)
2. Type in the following text and press enter.
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain user
You may need to wait 10-20 seconds while the command is processed.
3. Close and Quit Terminal.
To check that this has solved the issue, right click a file and check