I just rebuilt my HTPC and I'm seeing the behavior that sometimes a video plays audio with a black screen, sometimes it doesn't play at all, just a black screen. I noticed that without audio, nothing else pops up on the screen when I skip forward, change volume or press info. When audio plays, search bars and volume bars are shown.
I'm using ROHQ. I have set the display frequencies to match the video source, but I had set things like 23.975 to 24 and 29/59 to 60. When I changed that to 23 and 59 things improved dramatically.
Over the weekend I had MC not return to Theater View at all, it just remained black. Alt-tab would show the preview windows but alt-tabbing to something other than MC just showed a flash of the other app, they wouldn't stay in the foreground. MC was unresponsive, Ctrl-alt-del showed the options for task manager, shutdown etc, but task manager woudn't stay op top either, things turned black again. I eventually just rebooted. This happened twice.
Another setting that I disabled may have had to do with it, in Theater View settings at the bottom there's something called exclusive mode. I had that ticked but disabled it because I wasn't sure what it did, it might have been responsible for MC not returning to Theater View after playing a video I don't know.
When I looked at the list of refresh rates, at the bottom is something like default behavior, which defaults to desktop settings. I had that set to 60hz, but then I noticed Windows/drivers preferred 59Hz. I changed that back to desktop settings and that may have improved the behavior as well.