I can think of 2 other options other than a system check with utilities. That is 1. You try another video player & trial it out as your default video player (it can also play many audio formats): VLC - (click on link) _ (choose nearest mirror site) as it has in-built codecs & is generally reliable. To see what formats it can play see http://www.videolan.org/vlc/features.html & to make it your default see the suggestions here Setting Default video app

2. Try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & #3 in Fixes for Limewire (sample image included.) But make a note of your settings b/c once you delete your LW prefs folder, the next time you open LW you'll need to reset your options.