Hi Joshua! I can’t reply to it so I’ll just thank you here. I got the update installed and thank you so much for your help! It is much appreciated 
It works now and also seem to run much, much smoother.
Just one little thing remains now, I have 4 displays on this system and I run the video on a LG HDMI monitor with a monitor split that also sends the signal into a TV inside the speaker box so the actors can see the Picture. The video will now show on the screen but when I start full screen mode, it goes black. If I try to go into full screen mode on one of the other monitors that splits through a VGA connection for the same reason, it works fine. The video works on the main movie in full screen mode when I’m opening the same Project in Nuendo 5.5. Any idea why this happens?
EDIT TO ADD: Just noticed that if I double click the video screen from full screen to, er, not-full screen mode a couple of times while playing back the Project, it will go to full screen with Picture. Is this a bug, or is it my setup?