Nobody took the bait on my original post. What happened to me sounds like a common problem.
I had an Nvidia graphics card.
The latest linux releases (I think I have this right) have moved graphics card initialization from the grub loader all the way down into the kernel, so login screens can be high definition and sexy. It doesn't always work on upgrades, especially so when Nvidia is involved.
So for me (after apt-get dist-upgread) I got the black screen of death. I could get a terminal screen with cntrl-alt-F1
I bought a new graphics card. Backed up all my use files, used a MacBookPro to download a new installation image, burned that to DVD and re-installed from bare metal.
Previously I had been running Mint Linux with Cinnamon. I had non-stop little annoyances with that system. No show stoppers. But it pissed me off constantly.
So this time I used a Mint/Mate distribution and (so far) I like it a lot.
If you get the black screen of death you might need to update your graphics card.