What's the matter? It told you twice, already, that there's an error in the LightWorks Rendering Engine. That would be the failure of Graphisoft to implement radiosity.....
I'd be restarting ArchiCAD and reloading the project, then resaving it with a new name.
Problem persists - a corrupt element that is illogically formed - the engine can't resolve it. Hide objects.
Problem persists - an impossible calculation - could be, like, 50 layers of high-refraction glass or something. Try a normal method rendering - this will have NO transparency. Refraction is a big resource hog.
Dwight Atkinson