Your mac thinks the file is a limewire file. Download "File Buddy" and use it to change the file type at the root level. Make it a quicktime (for mp3s) or stuffit (for programs) file, then it'll open.
Limewire 17c solves this problem.
Took me while to work it out too, but its all in the archives on this forum if you wanna look.
Andrewk4