I will try to help. Hopefully you can provide some more info? First can you provide the os version and is it up to date? Also are the drivers for your video cards up to date or more specifically what driver versions are being used now?
Second this move from a earlier version of Adobe premier pro to adobe premier pro cc did you keep the same exact settings from old to new?(specifically "Mercury Playback Engine GPU Acceleration (Open CL)--video card settings etc.. This type of problem from my experience is a few/five years in the past but i will; once i get a break( 30 minutes from now) from my work i ll will mount some older reference storage drives and take a look for good info and maybe an answer for you! Oh another question your hard drive what its size ??how big did you set the scratch disk? how much space on this drive is used and how much is unoccupied? later i will provide some more input. Hope your day is getting better!