There is actually a problem with SC2. The CPU is the one that generates the frames during the cutscenes. It is actually a sort of glitch or a part during the making of the game, gone entirely wrong. Similar problem was there with Mafia 2. The Physx part is usually supposed to be done by the GPU, but in that case it was the CPU.
But then again, you have a 2600 K....
Try and do what 'plznote' told you to do.