Slow-motion = unplayable game

So, I am playing in the Hinterlands, and the game is runnig smoothly, up until I reach the Horse guy. When I start talking to him, suddenly the game goes into such a low fps its like slow-motion. The characters move, but they move like they are in a matrix movie, literally one step takes whole seconds, its unplayable.

I installed the NVIDIA beta driver and the game somehow got fixed. It began working a bit better, still there was a minor delay in motion, most noticeball on horseback. And then I go to fight the Hinterlands dragon, very undergeared and underleveled, and it happens again. The fps or whatever drops and the game starts working again like its in super slow-motion, completely unplayable.

This effect does not goes not go away when I travel to another location or map, like from Hinterlands to Haven. Nor does it go away for me after played time. Even more, even the in-game menu works with such great lag. The lag goes away in the Main Menu of the game. But return upon loading ANY save game. Even from before these problems.

What can I do to fix it? I am running the game on Medium, and it also happened before on Low.

My specs:

GPU: GeForce GTX 560M

CPU: Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz

Memory: 16.00 GB RAM

Driver version: 344.75

Operatin System: Windows 7 64bits