Do you use the Describe button in the LW Library window? If yes, don't. WMP doesn't like it. That's why the mp3's will no longer play in wmp. You'd need another player to play them. But you should be able to burn them fine if using another burner program like nero or roxio. Even iTunes.

If you only want to find wma files, then put .wma at the end of the title in your search.

What you could try is removing those songs from wmp's playlist & then re-adding them. It prolly won't work but worth a try.