Hello Laszlo!
I downloaded the 8.1 update and couldn't get it to load. I emailed Graphisoft and they said the update wouldn't work with the student version. I have since purchased ArchiCAD 9 Student Version, which loaded beautifully. Guess I'll be back to this forum if I have trouble in 9.
Incidently, the original problem, fill colors disappearing, has itself disappeared!
Thanks,
Bob