I'm in 8.1. The first project was created in 8.1, the 2nd in 8.0, but opened in 8.1. Now that you mention it, I don't recall having this problem in 8.0.
Taking this a step further, I just opened someone else's 8.0 project in 8.0. Initially, changing transparency in 3D from off to on, then rebuilding resulted in the glass becoming transparent. But then reversing the process, no effect unless I select the glass, open tool settings, ok; then glass becomes opaque. The only difference is the glass transparency is the default 90%, I've adjusted the transparencies to various settings on the other 2 projects.
I am regenerating the hidden line fly-through, and had to select the doors (in 3D window), open & close, to get the doors to appear correctly. I have run across a few others in ArchiCAD Talk having problems with doors appearing as solid blocks, but haven't had time to follow that thread.
