Just wondering as you said the scene worked in the earlier Alpha, so was thinking it was maybe created and saved back then? If so, something may have changed in the way things are handled (internal stuff - that would be one for the devs). For me, deleting the light material and creating a new one solved the problem, but it wouldn't render otherwise, it just froze. Cinema 4D R19 here. Note, I mean when the scene was created and saved, not when it was rendered :)