Here are two viewports rendered with OpenGL (top) and Renderworks (bottom) on a client machine (left) and the same viewports rendered on my computer (right). The client is quite desperate because he is getting these black backgrounds in both OpenGL and Renderworks intermittently. He is also seeing white (RGB 255,255,255) areas in rendered images turning black on his computers but nobody is able to reproduce the behaviour anywhere else. Any ideas? Thanks!