Unstable after upgrade to C8

Hi everyone. Hope you have better weather than we have here in Chicago! Cold, windy and raining.
C7.5 was working like a dream. I upgraded to C8 and boom.
Every click freezes the whole machine for 5-10 seconds. This is really annoying, making C8 almost impossible to work with.
The paradox is that right after upgrade everything was working fine for good few hours.
After new restart the problem started.
Does anybody has similar issue? I’m running brand new machine with win 8.1 Pro 64 bit. Is this windows related or something else?
I really, really like new options but stability makes it not possible to use.