Many GUI Programs suddenly not appearing on El Capitan I was adjusting Accessibility options and then poof the following programs disappeared from view.


Finder
Google Chrome
Atom (editor)
Opera


Safari is the only guy still working. Note: the processes for Chrome, Atom, Opera are still there: but the GUI's can not be shown.  I have checked in other spaces: there are no apps in the other space.

I also logged off and even restarted the computer: same behavior.  I reset the accessibility settings. No dice. What might be going on?
The issue was I had inadverently had both VGA and HDMI connections from the mac to the same monitor. It was actually working fine until I twiddled with the accessibility options. 

Now why it is that the accessibility changes caused some programs to decide to migrate to the unviewable display?  Not sure..