After getting a production 99% finished, my preview window has gone black. I stll hear the audio, This is a short 10 minute project with two video and two audio tracks. I've done a <cntrl><shift> to reset the program, and can find no setting that seems related to the problem. Other projects still display just fine. Though it's difficult to see a change on the menu, I've toggled the "mute all video" button several times, with no effect. I am able to preview items through explorer and the media bin.

The sad thing is, I had this happen one before, and got it solved through phone support no longer available for this version, but I don't remember the solution!!!
Help!