Fixing “Bluetooth: Not Available”

Recently my built-in Bluetooth stopped working on my PowerBook. This may have corresponded to a bizarre request for a “System” keychain password on startup that I was unable to answer and haven’t seen since.

Anyway, the fix that worked for me:

1. Delete ~/Library/Preferences/com.apple.Bluetooth.plist
2. Unplug USB devices (though I didn’t have any at the time)
3. Shut down
4. Wait a tick
5. Start up