Have you been here: http://www.portforward.com/apple/Air...forwarding.htm

You'd need to set up a static ip & forward port 6346. You might also need to make changes within LW I'm not sure. See: Manual port forward instructions & sample image & 2 posts after that.

For a start, set LW to connect manually. Go to LW's preferences>Connections & untick option to start on startup & press Apply. Then go to File>Disconnect. Wait few mins & then go File>Connect. Give it some time to connect.