How do I remove duplicate "Open With" context menu items in Finder.app? For whatever reason, the "Open With" context menu in Finder is always listing every app four times (exactly). 



I've read about (and tried) rebuilding the Launch Services database to restore the context menu to its initial state, but nothing seems to work. I've also used Onyx.app to clear user and system caches, but I'm still left with four repetitions of each app under the "Open With" service. I have restarted the system a few times just to be sure it was not some temporary corruption of the list.

I'm running OS X 10.6.6 on a 2011 17" MacBook Pro with a fresh install of OS X (i.e. I didn't use Migration Assistant.app or a Time Machine backup). I did, however, sync all my preferences and other files using MobileMe like I always do, so I imagine it's feasible that a preference file somewhere is causing problems? I didn't notice whether this was happening before or after my MobileMe sync.

How can I fix this so one app shows?
Since this problem happens at System Level, I'm not sure if these steps will do any difference.

I assume that, like you've said, you've rebuilt your LaunchDatabase. Just in case: 



You can try the Command Line version of the above (In a terminal):

/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user


Additionally, Default Apps is a nice and free System Preference pane to control default apps (based upon extension, type, etc.) You can pretty much see and associate everything from there. It should at least give you a hint whether the problem is in the association or the finder is doing something funky. 

When did this start happening? Did you install something? I see you have Xcode 4, did you get it from the App Store or you have a Developer Profile and got it via direct download? Was this happening before? Does this happen with every type of file or only some specific ones?