There are two possible causes.
The first is that you have a codecs issue with this file. To check on this download the free VLC player with built-in codecs. If that can't play the file then we can consider the second possibility; that is: the file is a faked one hosted by those who want to discourage people from downloading files via the Gnutella network.
http://www.videolan.org/vlc/(click here) 