How do the tracks look? Identical?
It is very well possible the clip has a thumbnail baked in, and that is displayed as a track, but omitted in playback.
There are two mono audio tracks, but they probably belong to the ‘good’ video.
You could use FFmpeg to strip the second track, or perhaps turn off one of the tracks in QT7 pro.
(Or delete it, and do a ‘save as’ to flatten it without the track.)
If it plays in the viewer, it can be rescued without any quality loss.
Bouke
http://www.videotoolshed.com