Make sure your 'QuickTime for Windows' prefs are set to read ALL quicktime file types. To do this, open quicktime, go to edit, and Quicktime prefs, and 'file type association' and check all of the boxes. If this doesn't help, then you might check the file type. You may need to resave and reburn your movie as a different file type.
try reinstalling, then when the preferences come up set it to play the file exension of your movie. If this doesn't work try playing it on the Mac in your studio again to see if the file is corrupt