Finally I figured it out! I wondered what all those blocked incoming, UDP, port 1900, remote address 192.168.0.1, to “N/A” process names were. All I had to do was disable “UPNP settings” on my router. I don’t have any UPNP devices on my XP machine, and the service is disabled as well. It was driving me nuts. So I'm curious, has anyone else encountered this? Under what circumstances would this option be enabled? My router is a D-Link DI-624.