SmashManiac: For those experiencing this problem: I upgraded to ScummVM 2.1.1a and it fixed the issue for me. Hopefully GOG will upgrade ScummVM in their installation package as well soon.
I should note that we (ScummVM) are still looking into the issue and, personally, I have some clues and ideas to fix it further.
For the moment I would suggest:
- Install the game on an internal hard drive (rather than a external USB drive)
- If playing in Windowed mode, not to move the game's window around on your Desktop, while a video cutscene is playing.
- Not to Alt+Tab away from the game screen, while a video cutscene is playing,
- Not to otherwise "pause" the game while it's playing a video cutscene (eg by bringing up the ScummVM in-game menu with Ctlr+F5).
If all goes well, I expect we should have a better / full fix by the next major ScummVM release which should be 2.2 -- along with more fixes some planned and some already implemented since 2.1.1a, and more restored content :)