When I turned on my G4 minitower, instead of booting into the GUI, I got a Darwin/BSD login and my password wouldn’t work. If I booted from the other drive (which has Jaguar installed), everything was normal and I could access the main drive. I repaired the drive & repaired permissions successfully.
The next time I tried to boot, the same thing happened again. I assumed it was a corrupted netinfo database and deleted /var/db/netinfo. That would normally cause the setup assistant to run when I rebooted, but in this case it didn’t.
I ended up re-installing panther as an archive install and recovered my user directory from the Previous System backup. Everything is back to normal now, about an hour and a half later.