Random Freezing During Browsing Or Work?

In short the notebook freezes randomly, while I am working with After effects, browsing the net with chrome, using excel. Just average desktop work. Sometimes the freezing happens a lot and sometimes it just doesnt happen at all. It doesn't happen when I am watching a movie or playing a game. The freeze is weird. The computer looks like it is frozen, but the mouse cursor still works and everything still works. because when it unfreezes after a minute or so, I am on the window where I have clicked on the task bar, or alt-tabbed to. I can stop the music, whatever, everything still works. A while back, I was working in After effects and I had Mocha open at the same time, the notebook was freezing like mad, I was getting mad and taking out my frustration out by clicking like mad all over the screen, then i discovered if i clicked on the mocha icon in the task bar, hey pesto, screen unfreezes. This doesn't work with any other app open.

What the hell is going on, it's driving me nuts, I don't want to have mocha open all the time, just so i can unfreeze the screen. I have already tried so much to troubleshoot this, I have run out of ideas. reinstalled, tested ram with mem test, tested gfx card, latest drivers, scoured event viewer for errors, swapped hard drives. checked latency, all ok. Dodgy rouge software maybe I don't know.