What type of files are you trying to launch? And is that the windows, linux or mac verson of the beta? I've successfully launched video files but haven't tried audio as yet. It has been reported that audio files don't launch properly in the beta.

I take that back, I just successfully previewed an audio song using iTunes on a mac. But that was odd. My media player is enabled but it played on both iTunes & LW's media player. I stopped itunes but it still played on LW's media player. (ie: It played on both simultaneously!)

I also launched songs from my Saved Files folder & my shared folder & both played fine in LW's media player.