What type of mp3's are they? Either they are corrupt or LW is having difficulty playing them. The new beta version of LW 4.1.7 has improved mp3 support. And yes there's a Pro version 4.1.7 that can be dwnlded from your personal dwnld page (bottom of page.)
Alternatively, why not set iTunes to play your music. You will need to go to LW's Prefs-Player & Untick the box for Use LW media player. Then your default mp3 player will play the mp3's instead. That will probably be iTunes.
The image below shows the option box ticked, you should untick it if you'd prefer to use another player. |