Make sure that the Windows firewall is off (it will conflict with the Norton firewall). Have a look at the links below for info about configuring Norton firewall.
PortForward.com - Free Help Setting up Your Router or Firewall
http://www.gnutellaforums.com/226610-post6.html

If that's no help, please give us your details.
System details - help us to help you (click here)