so far, the main thing that locks up c6pro is when I try to edit the dynamic hair shader tree. v4.1 will open o.k., although it is slow. AFAIK I haven't done either of these: 1. activate V4.1 on your desktop 2. make sure you are on the small or medium screen size. NOT the big one. but I don't know what either of them indicate. perhaps the latter refers to the largest monitor resolution in pixel dimensions. I have mine at an intermediate setting. I don't see any way to turn off OpenGL, in case that's causing problems for some users.