I've tried Opensuse 13.1, Kubuntu 14.04 and every other distro I can find that supports KDE and this issue recurs in all of them. This happens with or without the video driver installed. I run a Lenovo y500 with dual gt650m video cards. Ubuntu 14.04 with unity desktop looks and works fine without this issue.
It's a tough one to explain so I have made this short video to show the issue. Note the window borders and how they pixelate / break when dragging.
If anyone has any idea as to how to fix, I'd be eternally grateful. My setup is HDMI to an external monitor but this issue occurs on both the laptop screen and the external. I've tried turning off desktop effects with no change as well as messing with nvidia-settings.