I had no idea this issue was so complex and also so abstruse! Surely it must pop up all the time - every time somebody buys one of these products like the cycloramas or Alien World (my first encounter with the problem) and then tries to render it with Ray Tracing turned on. Most Poser users do not have the expertise of the people on this board; do they just give up? Do they, maybe, find this board and ask the question I asked, thus irritating those who have seen it all before? If this is the case then perhaps there should be a sticky thread with a definitive answer in it.