If your flash file works correctly when you test the movie in Flash, but not once it is published, check your Publish Settings.

While modifying a flashcard example application I downloaded from Flashkit.com, I noticed that in development, using "Test Movie", it worked perfectly, but once published, it had odd bugs.

On checking the publishing settings, I realized it had defaulted to Flash Player 7. Once changed to Flash Player 9, it worked fine. Apparently, some of my modifications relied on features that Flash Player 7 does not support.