Try changing the file extension to .3gp ( 3rd generation mobile video ).
Mp4 s copied from cell phones to OSX often give ‘An invalid sample description was found in the movie. ‘ Changing from .mp4 to .3gp allows OSX to play the movie.
This supposedly works on Windows as well but several people were unable to successfully change the file extension in Windows. If that doesn’t work try changing the extension to .3g2.
3gp is a stripped down version of mp4. In addition it contains information about the size ( height and width) of your video and the bandwidth speed of your phone. Supposedly QuickTime and RealPlayer play them, but good luck getting that to work.