First you don't need a firewall on osx, uninstall it or desactivate it completly to run LW. Second, if that doesn't work, maybe the company blocked Gnutella traffic. If they do, there is not much you can do. I'd try another Gnutella app as Acquisition just to confirm the problem is not on LW's end.
http://acquisitionx.com/ (the author of this app is an *** and abuses LW gpl liscence, so don't promote it
, only testing purposes. )