Over the last few years I encountered the following QuickTime 7 error message several times while trying to play a file:
The cause of this message is a broken Resource Fork which is stored within the file’s extended attributes. This error often occurs if the file is or was stored on a network drive or an external disc. It also affect all applications that build upon QuickTime 7’s API. To verify if a file is unplayable because of it’s Resource Fork just try to play it with VLC. It should work fine. If so, it can be fixed.
To make it easy to repair such files I wrote QT7 EA FIX. Just launch the script and drop the broken file. The rest will be handled automatically and you should be able to play the file afterwards.