I've had a very similar problem to this with intense slowdown occurring every 30 minutes or so.
I had found a temporary fix in which I had to close any dialogues and then minimize and then un-minimize C2.
Before that it was just closing down C2 and restarting it.
A few days ago I switched it so that C2 runs off of my dedicated graphics card instead of the integrated one and I don't think I've had to minimize/un-minimize since then, so I'm calling it fixed.
I'm hoping this helps someone down the line cause this was really frustrating having to deal with this problem for years.