Try another player. QCD will play all audio types & is Free & has built in codecs: http://www.quinnware.com/
You may even decide to make this your default player. (Right-Click an mp3 file on your desktop & choose open with...QCD & choose always use...)
If you do you can disable LW's media player (Tools>Options>Player untick option box & press the Apply button.) Then everytime you preview or launch an mp3, QCD will play it.