There is apparently a bit of a bug that if you change the id3 tag using LW after having added the song to WMP's playlist, then wmp struggles to read it. This is odd. This is a bug b/w LW & wmp.

Alternative players ... well there's so many. A good one is QCD: http://www.quinnware.com/ which has in-built codecs but still you can add more codecs from their site. It plays everything.
Then there's iTunes, like or hate it, its strength is that it has its own music library. So if you add a song, it goes straight to iTunes own music library. It has other strengths also. It also allows the new downlds to be listed as a LW playlist within iTunes (but this is only a playlist - you need to add the songs separately to be added to iTunes own library.)
iTunes: http://www.apple.com/itunes/download/