However, once I had finished loading I tried looking around the usual with the middle mouse button - with little success (or none, actually - the button does not work).
Reverted to the old files (mostly 5.2. something and NA - DialogTree 1.0.0.0) again, and it worked as it should again.
Didn't delve further into it/test one file at a time, since I was dead tired yesterday because of almost no sleep the night before. Probably an old man thing.