Are you getting a corrupt file message? Have you tried disabling the LW player & making something else your default player? The LW player is pretty weak & can suffer badly if you're doing a lot of dowloading!

Otherwise, have a look through these threads
http://www.gnutellaforums.com/showth...oads+corrupted
http://www.gnutellaforums.com/showth...oads+corrupted
http://www.gnutellaforums.com/showth...oads+corrupted
(you can try LOTR's experiment in the thread above & download a magnet link file... see if it's corrupted too)
http://www.gnutellaforums.com/showth...oads+corrupted