Well, well, well... According to this I need a new wireless router because my cable modem's firmware got upgraded.
Super.
(Honestly, I'm just happy I found the information I needed. Comcast technical support was useless, of course. I'm not blaming the tech support people -- They are just trying to get through another day at their their jobs just like everyone else, and they can't help it I know just enough to get myself in trouble sometimes.
Still, though... If somebody figured out that the firmware upgrade causes bustication with routers equiped with slow speed WAN port, you'd think the broadband providers might want to disseminate that info.)