-- William Gibson, All Tomorrow's Parties
Updated selene (my PowerBook, PB12A) last night. Seemed fine. Also updated helios (Mystic, dual G4 500), and it has displayed no weird behavior.
This morning, I woke selene up to check email and do some admin stuff. I was connected via wlan via AirPort. Had Keychain Access open, and was in the process of opening TextEdit. They both SPOD'd, which is really, really weird (never seen it happen before), so I killed them, restarted KA -- and all my keychains were gone. KA keeps references to files, and doesn't actually try to manage the files unless you insist, so the actual keychain files had not been touched. So I went to re-add login.keychain (which is kind of important), and it failed silently. At this point I'm more than a little annoyed, so I close all my apps and go to log out.
The machine boots itself into single user mode. Awesome.
After failing to log in a couple times, I hardboot it and it comes back up. I reconnect to our wlan network, and kick open some apps. They start displaying the same behavior. I kill them, turn off AirPort, and plug in a wire. Everything is fine.
So either someone has something unreported and is spamming at my machine via wlan, or Apple managed to fuck up AirPort somehow with 10.3.6.
As Adam said, "Occam's Razor."