I just wanted to post a summary of my problem where the latest X11 server on Tiger says that it can do stereo glx visuals, but any program that attempts to create a stereo window crashes. I tested with a non-X11 CGL program, and I get the same behavior. The problem is that my computer (Powerbook G4, OSX 10.4.11) advertises that opengl can do stereo, but it can only do stereo in full screen mode, not per-window. Since Apple's opengl says that it can do stereo, the X server sets up all of the stereo glx visuals. But just like the native CGL programs that I tried, any glx program that tries to create a windowed stereo visual crashes with an error because it is not full screen. I don't know if this is specifically a problem with Tiger or with older hardware. An old G4 tower with an ATI video card running 10.4 displays the same behaviour. I must have run into this problem before because I had set enable_stereo to false in my x11 preferences, but this option seems to be ignored with the recent X11 servers. Can you bring back the enable_stereo preference option? It should default to true it not set, but allow one to turn off stereo visuals if the older hardware wrongly advertises that it can do stereo. Thanks, Martin