I had a look at this http://www.i29.net/index.php?page=su...n=3&article=27
There is a chance the firewall is at the ISP with their wireless service.

Rather than just change the listening port, also try changing the connection port.

If still no go, try another gnutella program. A couple of others to try: Phex to see if you have the same problems. Where to get the “real” BearShare