Admin password no longer works

Upon startup, I enter my admin user's password and receive the error message "Doh, that password didn't work." Particulars: - I'm not "fat-fingering" the password - The password hasn't changed - I don't have caps lock on - Panther 10.3.3 on PowerBook 667 - VaporSec 1.0 (10.3 version I found here in the forums) - Vaporsec was working fine yesterday - I've repaired permissions on my OS X disk Suspected Cause: - Downloaded and installed Apple's Airport update today (it's the only thing that's happened to the system since yesterday.)