Antraxxx: I had a similar problem. At first, the game would only let me perform one action, after which the mouse cursor would disappear and I would have to Alt+F4.
I've tried the wrapper mentioned here to no avail. However, since screen transitions were instantaneous, I assumed it's a codec problem, so I replaced mine with the x64 version provided here:
https://www.moviecodec.com/download-video-codecs/cinepak-11/
(caveat: it's a self-extracting RAR which I extracted manually using Winzip. The file may be infected with malware)
After replacing the codec, the mouse cursor no longer disappears - I can play the game. However, videos are still a black box, with and without the wrapper.
Any ideas?
Strange to see that codec replacement was able to fix the disappearing mouse cursor for you. But the main thing is that it helped :) Unfortunately afaik nobody does seem to have a solution for the black boxes instead of the video for now. Fun fact: this is something I would try to fix using a different codec but even this did not help so far. The only thing that MAY help would be to uninstall all other external codecs you may have on your system to prevent them interfering with the ones from the game. Usually things like codec paks i.e. are never good and should be avoided.
Seeing how many people still are experiencing game breaking bugs it is a wonder for me how this could pass GOG's quality control which they advertize as being extremely cautious. If nothing helps you can always refund the game but then again I don't think that would be the ideal solution to the problem.