Have you tried port forwarding?
You'll need to set up a static IP address first, there are instructions within the link below.
http://www.portforward.com/english/r...4/Limewire.htm
Afterwards, you'll have to go to LW's tools > options > advanced > firewall config & choose the 'manual port forward' option (make sure you enter the same port number as LW's listening port) > apply.