See if this thread helps to get files to launch. It's long, but an answer should be in there.
<http://www.gnutellaforums.com/showth...&threadid=3294>

For 4-3 of the FAQ, those instructions apply to Windows. There is no contextual menu option to "Open with" for the Mac. The easiest way to get files to open with another application is to drag the file to the application or open it from within the app.

A more permanent method which applies to all files of that type is to go to the File Exchange control panel and click the File Translation tab. Make sure "Translate documents automatically" is checked. If you check "Always show choices when translating files" when you open a file that isn't assigned to an application you have, each time a listing will be shown of applications that should open the file. With the option unchecked the first time you choose an application that one will be used every time after.

When I am referring to files, I am talking about the downloaded files in the Finder and not in the LimeWire library tab. LimeWire 2 handles this opening stuff much better than the 1.x versions.