Instructions on how to allow LW access thru the most common firewalls is here:
http://www.limewire.com/english/content/firewalls.shtml Which firewalls do you have?
But if you have a high-speed modem/router wich has an internal NAT firewall then forwarding a port (6346 for LW) might also be necessary (opening a single port.)
What brand & model of modem/router do you use?