to the Gnutella Forums Dave666.
The LW Media Player isn't very good and has kinda been put on the back burner so to speak.
I would recommend trying an alternitive Media Player to see if that helps.
VLC
Media is a nice one to try. See Link
CODECs list for Movies/Audio/ Alternate players / Video help forums/ video-mp3 fixers
If you want to continue too try and use the LW Player, Go to Tools > Options > Player, and make sure the "Use LW Media Player" Box is Checked.
Did you try to Preview the Files while D/Ling ?? You may have found yourself some Fake or Corrupt Files which are Very Common on the GN. This Link may help.
WARNING: Viruses on network you should be aware of! (click on blue link)