Under 4191 I had a working OpenGL install. (TuxRacer ran beautifully, GLX gears of 6000 fps.) I installed 3123 and glx gears won't even run. (Missing/bad glx, but it's still in the XF86Config.
kahuna: Did you have the lockups under 4191? What motherboard/system/graphics card do you have?
PS I'm not using DVI or TV out, just plain old vanilla VGA. (Cathode Ray Tube and all!)