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For some time now I'm experiencing an annoying behavior under Mountain Lion:

While doing my daily work, the programs to open a file keep changing. For example, opening a PDF is switched to Adobe Acrobat Pro instead of Apple's Preview. PNG images would open in Safari instead of Apple's Preview, etc ...

If I open up the file and choose my program from a list and click the checkbox "Always open with" it works for a while. Same for get info -> Open With: ... "Change All". It works for a while but at some point (without restarting!) it is changed again over and over.

I already tried using Onyx, deleting all caches, rebuilding various data bases but still the same error.

I'm not sure when it all started but I have the impression that after using IronAdium (a hardened version of Adium using the sandbox features of Mac OS X) this might have happend.

Any help or suggestion on how to fix the file associations once and for all?

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You could try:

  • Deleting ~/Library/Preferences/
  • Rebuilding the Launch Services database with /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -domain local -domain system -domain user.
  • Using duti or RCDefaultApp instead of Finder to change the default applications.
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