I have Intel Quad Core Q9550 and GeForce GTX 260. I have just downloaded the Viewer 3.0. I can run the graphics setting for shadows, and for a while everything works fine. But then my screen will suddenly go black, and I don't see a picture until I uncheck the shadows box. Every time I try to restore shadows, my screen goes black. Does anybody have an idea while this works for a while (about a minute or two), and then goes wrong? Blimey - is this how the forums work these days? How ridiculous that I cannot respond to answers! Ok, turning off the VBO option does indeed prevent the black screen, so thanks for that. But unfortunately it also cuts about 60% of my speed, so it's not an ideal solution. Thanks for the help, though, to both of you.