[Cullen Hoback]

I have been suffering from this problem. My viewer would go black completely after random edits. It seemed once my project hit a certain size (not using proxy or optimized media) that the viewer would go black, or the frame would just lock. Audio would still play.
I have the latest everything. I called apple and they had no explanation. They tried having me reset the video card on the computer.
From what I can tell, this has something to do with there being a maximum amount of non-native footage that any one system can handle.
It may have something to do with using too much of a certain file type, until the threshold is reached.

My solution?

I broke my project in half and started editing the second half on a separate timeline, compiling them at the end.

It works.

If I could go back in time, I would never have started editing with this garbage program.