I originally had the router set up to start giving out DHCP at .2.150, but going with the Windows school of debugging -- when everything is set up right and it's still not working, start changing things that shouldn't matter and see what happens -- I changed it to start giving out at .2.100.

Then, with the router not plugged into the modem, the PC got .2.101 from the router. I plugged the router back into the modem and restarted networking on the PC and it grabbed .1.64.

I'll double-check what I have everything plugged into. Yes, it is a 4+1. If it turns out to be that, I'll be pissed at myself, but really grateful.