Closest thing to a router I have is a DSL modem:
SMC ADSL Barricade Router SMC7401BRA

But I doubt that's it, because this only started to be a problem after I upgraded my PC hardware (mobo, cpu, vid), and reformatted my HDD and installed WinXP. That's why I figured at first it was just the WinXP firewall being stupid. But, that wasn't the case. Anyway, I can't access that little chip in the DSL modem or whatever anymore because I can't remember the default user/pass or the IP to access it (my ISP doens't want me doing so anyway).