After viewing imbedded videos for a time, the video ends up going away, but I still have sound. (So I know it's playing the video.) Doesn't seem to matter what site I'm on, the video ends up as a half screen or less, or black screen. I can shut down Firefox and restart it, and all is well again for a time. I get no error message since the video is playing even if I can't see the video part of it, and I can't seem to find any problems anywhere on the system that would be causing this. Since all comes back to normal with a restart of Firefox, I thought this would be a good place to start looking for a fix.