Boot failure

[Identry]

Well, the bad day has come... My primary server won't boot. I have
backups of databases and user directories, but I need to try to get
this server back up again.

During the boot sequence, it freezes at the statement:

    Trying to mount root from ufs:/dev/mfid0s1a

I tried booting into single user mode, but same issue (of course).

I don't want to just start hacking at this for fear of making things
work... what is my best, most conservative next step?

-- John