Sorry for the long wait to reply. Work is very busy. I've downloaded and looked at Acrylic's output. I discovered only that of my two access points, one was not running. Normally, I set it up so that one runs the 5Ghz network, and the other runs at 2.4Ghz. So I corrected that, shutting off 2.4Ghz on the AP that shouldn't have been running it, upgrading the firmware of the correct 2.4Ghz AP, and making sure its settings conformed to Apple's official settings recommendations.
Now I have two APs visible in Acrylic:
2.4Ghz, supporting b g n up to 144.4
5Ghz, supporting a n up to 450
Both show only WPA2 PSK-CCMP support.
No change as a result. It may actually not disconnect after all, but it can't maintain a fast connection. For starters, I can't connect at higher than g speeds. As others have experienced, it won't connect to the 5Ghz access point at all. When I first connect to the 2.4Ghz AP (located in the same room as me, zero obstructions), it linked up at 48Mbps. My Macbook Air 2011, powered up and running for several days and running Win7-64 via Boot Camp, was connected at over 100Mbps. As I write this post, my MBP's connection speed has dropped to 1Mbps. So to post this message, I will disconnect and reconnect. Having done that, it went back up to 36Mbps, then to 54. But it won't last.
My netsh wlan dump output is below. Not much there.
# ----------------------------------------
# Wireless LAN configuration
# ----------------------------------------
pushd wlan
# Allow filter list
# ----------------------------------------
# Block filter list
# ----------------------------------------
popd
# End of Wireless LAN Configuration