One option is to port forward your device. See PortForward.com - Port Forwarding Limewire on the Linksys WRT120N. Remember to set up a static ip address first before you actually forward a port on the router.

For LW 5's settings, see Manual port forward instructions & sample image. The one on the previous site shows a LW 4 example, not LW 5. If you download torrents also, you should probably make this port the same also.