You know that upgrade that seemed like such a good idea? From 14.04 to 16.04, first, then 18.04? Well...let's file this under the heading "things that should have been left alone."
I finally clicked the "version upgrade" button, which said it would install 16.04. Brilliant, I thought! Just what I need.
It started cranking away, and I watched happily as everything went as smooth as can be, from start to finish. Then it prompted me to restart the computer.
This isn't Reddit, right--so I can't freely drop f-bombs everywhere? Too bad, 'cause they're called for.
After getting the pretty Kubuntu logo, I got a blank screen where lines of text started appearing. Something about CIFS...error connecting to socket...aborting operation...failed with return code -115. Mount operation failed. A bunch of USB-related errors, ending with 'unable to enumerate USB device.'
And that's where it hung. Retried several times. Checked its boot and setup options; everything was normal.
My Kubuntu buddies have since let me know there had been major problems doing version upgrades from 14.04 to 16.04--and that it was not recommended. I--having been in a cocoon for awhile--had no clue. And after umpteen *nix OS upgrades under my belt, starting with 5.25" floppy drive installation media, I can't honestly say I even thought about checking first. I mean, who knew?!
I've reinstalled 14.04 and will finish cleaning up/tweaking things tomorrow.
I'm glad I'm as rigid and set in my ways as I am, because in this case wiping / and reinstalling the system there was all I needed to touch; my /home and /data partitions are sitting pretty with no data loss.
I'm pissed at myself for not researching this--even though, in my defense, I'd never encountered problems with system-offered version upgrades. First time for everything!
I am NOT pissed off at anyone else. I'm a big girl and take full responsibility for this fiasco.