This is not the normal "black screen"issue and I was shocked to eventually find out why. The normal advice of reconfiguring Xorg didn't work. Even booting into "Recovery Mode" did not help.
Here is the short end of the stick that fixed it:
sudo apt-get install mdm mate-desktop-environment
Yes you got it right, mdm and the mate-desktop-environment / gnome were somehow uninstalled. This must be whe........
Cannot even "Browse Network" when clicking on "Windows Network"
Unable to mount location
Failed to retrieve share list from server: No such file or directory
[2017/02/14 00:16:44.271314, 0] ../source3/nmbd/nmbd.c:58(terminate)
Got SIGTERM: going down...
[2017/02/13 17:35:41.797944, 0] ../lib/util/become_daemon.c:124(daemon_ready)