MacFr: I think the link in your QNAP post that goes to the WDLXTV forum is the most telling.
In that thread, there was a process running on the network SOMEWHERE that caused the DMAOSD to lose contact with the RENDERER.
On the WDTVs, DMAOSD is the "User Interface" process. The RENDERER process is what actually processes and displays media.
When DMAOSD invokes the renderer to play a movie (regardless of where it comes from), DMAOSD basically "clears the screen" of all UI elements and gets out of the way, and let's the renderer run the show. DMAOSD normally only gets involved with the screen during playback if the user brings up the OPTIONS menu or the status bar or whatever.
In the post you linked, DMAOSD threw out an error saying it had lost contact with the renderer. If that happens, it has no longer has any way of knowing what the renderer is doing. If you then press STOP, the normal menu UI will be brought back up because DMAOSD has to assume that the media DID stop. But since it can't talk to the renderer, it cannot actually tell the RENDERER to terminate the playback.
Therefore you get both the movie and its audio on the screen underneath the regular user interface.
So whose fault is it? Well, I believe it's ultimately WD's issue for two reasons:
1- The DMAOSD process losing contact with the renderer process should be handled more gracefully. If it needs to, it should just terminate the renderer and restart the process to restore communication. That would not ultimately fix your problem, because you'd suffer from aborted playback all the time. But at least your box would remain "communicative" and functional.
2- WHATEVER it is on your network that's CAUSING that broken process should be handled gracefully.
So, you're pretty much stuck at this point with two options as far as using the WD is concerned
1- Wait for a fix. It might be a LONG TIME, if ever, because it appears to be a rather rare issue.
2- Track down what's happening on your network and eliminate the root cause.
My guess is you have a process running SOMEWHERE that's sending broadcasts or bad packets to the WD using the same network ports the renderer is using.