I must say when I tried to preview a file in the downld list it didn't play. then I went to the Librar & launched a file from a shared library & it played fine. I went back to the download window & tried to preview again but this time it launched without problem.

Do you have LW's media player enabled or disabled? If it's disabled then your default mp3 player will attempt to launch any files. For iTunes that means it may import a partially complete file. That's why I prefer to use LW's media player for previewing & launching. If I want to listen to music then I open iTunes & play what's already in its library. I'm not sure, but either QuickTime or iTunes might have difficulty with some incomplete files.

Are you sure iTunes is your default mp3 player? Select an mp3 file in the finder, then hold down both apple & i keys & what does it say under the Open with... section?

You might need to try previewing button more than once. Try as I did to get the LW media player active.