From what Iv read the belkin router should have firewall settings and an option to disable you click apply and it should work.
Does your router look like these settings:
http://www.tuneld.com/_images/icq/ro...ess_server.png
and are you port forwarding halo like the example in the pic with the ports I stated before?
also if you have more than one comp on the network have you port forwarded to the correct IP?