Update: yesterday I spend a good deal of time reading the wireless toubleshooting sections at the netgear site. I print off several documents and download their "beta" drivers (which, apparently, address some issues with SP2 and WinXP).
Anyway, I get home, fire up my laptop and... lo and behold... it connects just fine. Connects fine for the rest of the day. Connected fine before coming into work this morning.
In short: I have no idea what's going on.