Now I just did a quick flight out of Ketchecan Alaska with the default Beaver.
I am getting black buildings with some good graphics on the boats, cargo and some ships.
I doubt this has anything to do with your graphics card. Make sure you activated the SDT_Object_Library before any other MoCat scenery areas. It should be below other areas like Ketchikan Alaska on the Scenery Library list. This is how mine looks.

You can select an area &











