I went from my old Eizo monitor (1920x1200) to a new one (4k) and was very happy about the huge amount of space that I suddenly had. - I fired up Cinema 4D R18 with a simply Vray 3.5 scene (just two simple objects for shader testing and a physical sky). Unfortunately Cinema 4D froze almost immediately. - Next I opened Cinema 4D with a blank scene, changed from full screen to a slightly smaller window and loaded the same Vray scene. That worked fine. As soon as I chnged to full screen -> bang! I have a Quadro 2000 graphics card, which is some years old and wondered, if this can be an issue. I went to the C4D preferences and looked at the OpenGL Antialiasing settings. They are at 8 by default and I switched them to None. Now there was no more freezing and everything went smooth so far, even in full screen. Honestly with 4k I don't care about the Antialiasing in OpenGL. Just wanted to state this here, in case someone else has a similar issue with an older graphics card. If your C4D freezes at hires, just try to set the OpenGL Antialiasing in preferences to None.