If you're using LW's media player then it's probably b/c LW is too busy to put many of its resources toward the media player. You can disable LW's media player so your default media player plays instead. Go to LW's menu Tools>Options>Player & untick option & apply. But you'll need to re-open LW before it takes effect. If you don't have a reasonable player then try either QCD (click on link) or iTunes (click here) which both have in-built audio codecs.