What player are you using? If you're using the LW player, it's not very good. Disable it (tools > options > player) & use another player.

If you're using windows:
In LW's library, click on Saved Files then click Explore. Once your saved folder's open...right click on a file > open with > choose program. Choose a player & see if the songs play. If you want to make that player your default, tick the box to always use the selected program to open files of this type > ok.

If songs won't play using other players, but your sound's ok on the computer & CD playback works...they might be crappy files.