Just ran an update, and restarted from the Software Updater. Computer failed to reboot, and would not reboot after several attempts. I was able to boot into Ubuntu Mate 16.04 which I have as dual boot, for this kind of thing. there I was able to do two things. One change the graphics drivers back to the Nvidia Drivers, and also to properly shut down the computer. I’m not sure which of those solved the problem, but if anyone else runs into the same thing, you can try this.
I have had this problem before when updating/upgrading, which is why I now have two versions of UbuntuMATE ready to go on the same computer. Just FYI anyone with similar hardware may want to be prepared with a similar method.
Nvidia 980 Ti graphics card
AMD motherboard
Optoma projector monitor