Matthias, I get the same rendering issues. I used to be able to fix it by toggling the Show/Hide Models (F12), but that is no longer refreshing it. This screenshot was taken using the scene in Tutorial 8 with the supplied rule (massmodeling_03.cga) and the self-made rule from page 15 (myMass_03.cga). The buildings do not show the default grey color and the setbacks do not show up as green. The default style does show the color. You can see in the log screenshot more details.
ATI FirePro V4800 (FireGL)