I was getting the exact same lovely boot failure.
I ended up using the auto-upgrade to restore myself back to normal.
The REcordings were inaccurate and needed some manual cleaning, but hey that's a small price to pay for where I was a moment ago.

If I'm reading this thread right, I think it's sound advice for even new installs to run a backup after they've finished their configs and tweaks and have things running well. That way, down the road should some nastiness hit, they can use an auto-upgrade to "rescue" the system.

Yes, that's what it finally took, right down to the "tidying up" afterward.

I'm adding a crontab to run the backup script in the middle of the night every few days, too...

Should minimize the damage if something goes wrong, which is really rare (my own poking around is the usual source of my woes!)