As for now, there is no encyption option in LW, sorry.
You could try to change your listening port in LW and add it to your fiewall exceptions.
In LW go Tools>Options>Advanced>Firewall Config and change there the listening port to a higher number (like 64049, 65255, 47058 or something like this).
On how to configurate your firewall, please read the following link:
http://www.gnutellaforums.com/showthread.php?t=51361 