I got the same problem.
I am using the Version of PowerDVD which came bundled with my LG Bluray drive. At first it was unusable, with no sound and a heavy pixelated greenish image from bluray.
Three days ago i updated PowerDVD, an now it performs marvelous...except for frequent monitor "blackouts". These are between 30 seconds to 5 minutes apart from each other. The screen goes completely black for about 3 Seconds, and when the picture comes back, playback hangs for additional 2 seconds.
Sound keeps playing through this, an after the hang everything is back to normal, until the next blackout.
Hardware is ati 4850 (no difference using catalyst 9.10, 9.12, 10.1) connected via HDMI to a LG W227 Display.
I do not think this is a HDCP issue, as it happens with DVD playback too.
The error occurs during playback, when playback is paused, in windowed mode and even while paused, windowed and in the background. The whole screen just goes black.
I think it occured more often with folding@home:gpu running (high gpu load), but the playback between blackouts was steady. Without FaH gpu usage never exceeds 10% during bluray playback.

I was planning on purchasing PowerDVD ultra to use surround sound, but at the moment i am assuming this problem would occur in ultra too, so I would appreciate a solution.