Tru64 v5.1B dsfmgr boot failure

Symptom: Tru64 v5.1B (probably any 5.1, maybe 5.0 as well), fails to boot with errors similar to the following:

     Restoring saved hardware configuration data . . . Done.
     dsfmgr: ERROR: cannot open and read file /etc/dfsc.dat : Bad status file data/ft
     dsfmgr: ERROR: cannot open and read file /etc/dfsl.dat : Bad status file data/ft
     bcheckrc: Device Naming failed boot configure or verify.
      Please correct the problem and continue or reboot
     INIT: SINGLE-USER MODE

You get left at the maintenance-mode #. Could theoretically happen after some system-maintenance event. I've seen it after a 5.1B reinstall on a DS10 466Mhz. Careful use of Google led me to someone else (in China?) who had the same problem. The link is to the original page, with the interesting notes below that...

http://bbs.chinaunix.net/archiver/?tid-250334.html

1. dn_setup -init ##initialize the device name databases
2. dsfmgr -K ##recreate all the device-special files
3. bcheckrc ##check and mount local file systems
4. init 3 ##continue startup to runlevel 3

Things that did not help:

1. disklabel -z /dev/rdisk/dsk0a #followed by disklabel -rR
2. reinstalling Tru645.1B