Well, shit.

I tried upgrading my AP's firmware. Seems that it just came out. Then the Vaio could no longer maintain a connection for more than a second or two. So then I looked to upgrade the driver for the wireless card. Sony still doesn't have an update, but Intel does. So I upgraded to that and now I can connect again, and I get full throughput: about 21Mbps.

So thanks, folks. Now I just have to get past the wife being mad at me because I wasted the whole day dorking on the computer.