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When I run QuickTime to play a movie (let's say a .avi file), the movie loads but the movie doesn't play. I click on the triangle button in QuickTime to play the movie and nothing happens. If I advance the progress bar to some random point in the movie, the screen just shows a still image of that point in the movie. QuickTime just doesn't "play" the movie.

Strange thing is that QuickTime works perfectly fine in my wife's login on the same computer as well as when I log in to a "test" account on the same computer.

I have tried to delete what I think are the plist files for QuickTime in my log in. However, the problem still persists.

Does anyone have any further troubleshooting tips? I am happy to reinstall QuickTime but since it is built into the OS, I don't know if that is possible. If this is possible, can someone also give me a walkthrough of how to do this?

Thank you.

share|improve this question
Reinstalling QuickTime would not be useful in your case, as the same application package is used for the whole machine, and QuickTime works on other accounts. Can iMovie playback videos? I believe it uses the same playback framework, which would allow us to further trace the issue. – Nathan Jan 15 '12 at 3:41
I tried iMovie just now. It seems to work perfectly fine in playing back some holiday movie clips. – Ken Cheung Jan 16 '12 at 0:32
In addition, Apple's "Quick Look?" works fine with these videos. In other words, when I highlight the file in Finder, I can tap the spacebar and the video plays normally. – Ken Cheung Jan 22 '12 at 22:02

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