I'm running VMS 12 Build 1184 with no problems. I did something on my keyboard that made my Preview window turn black and Trimmer window totally empty. I've tried all sorts of things to get them back (like setting Preview to Secondary Monitor, which I have) but nothing works.
My video plays OK on the timeline; the Preview window shows the framecount changing; audio sounds A-OK, but the preview windows is black. Preview does display Grid and Safe Areas markers OK, although I always have these turned off.
The Start/Stop etc. buttons on the Preview & Trimmer windows seem to work, but there is no image displayed in them. Same results if I move the windows to my 2nd monitor.
What did I do to blank them out? How can I get them back?