OK so your XP firewall is inactive. Double-check your firewall settings here: Configuring Norton Internet Security If you still get a false incoming bug report see below.

You said your router utilises UPnP. Perhaps it doesn't work very well. Something is definitely blocking your incoming. Would you consider manually forwarding a port? Up to you!

If yes, see http://www.portforward.com/routers.htm where you will find instructions under SMC on the far right of the page. To do this you must have a static ip for it to work. Instructions are included to do that at the above link under your model.

Steps are:
1. Set up a static ip. 2. Forward port 6346.
3. Within LW: Manual port forward instructions & sample image & 2 posts after that.