Norton firewall is crap, and I don't trust it...
If you're using the iBurst desktop Ethernet modem, why not sacrifice an old PC, install Smoothwall on it, and be better protected than Nortons? Plus is, you get to have nice things like the Bandview monitor (view your bandwidth usage), web visit logging, dansguardian content filter (block pr0n sites, advert sites, bandwidth-wasting sites) and the such.
If you're really interested, and is in the Pretoria area, then I'm willing to come and demonstrate Smoothwall for you...
I can remember that Norton will complain about something like that, even though the traffic was harmless, but can't remember the specific details. Besides, it's a complex thingy, and I don't trust complex thingies, but rather something simple which you can enhance to suit your needs.
Regards
Unbeliever