So, having installed the 10.4.8 update, and yet not rebooted, I decided to reboot my server, as it was no longer responding to ssh connections.
Of course, this was at 3am, and the server proceeded to spin its wheel on the startup screen and not come back to the login window. Holding down command-V to do a verbose boot revealed that the console was getting
launchd: getty repeating too quickly on port /dev/console, sleeping
launchd: /System/Lbirary/CoreServices/loginwindows.app/Contents/MacOS/loginwindow port /dev/console exited abnormally: Trace/BPT trap
Fortunately I had a backup drive with a slightly outdated copy of the server’s boot drive. So rebooting off that got the mail server back. Fortunately the old drive was still readable even if booting was failing, and thus I could copy all the old data files off it, and restore the mysql files and the WordPress installs. Unfortunately the backup drive was too small to copy the gallery back onto it, so a symlink and some permission changes and almost everything was back up.
Livejournal feeds got confused of course and dumped some old articles to the feed. Oops. But otherwise pretty much everything was back up.
I’ll probably try re-installing 10.4.8 on the drive and see if that fixes things.