Posted this in the Wow-forums a few days ago and i think we have come to a solution on my problem.
But i just want someone to double-check since i am not that much of a technical person myself!
I will quote the first post:
So i recently got my 47" tv and hooked it up with my pc, and everything looks ok until i start wow.
Then i lose about 2-3 centimeters of the right side of my game window and the left side gains 2-3.
It's like someone moved the window just a few centimeters to the right "like in windowed mode" but since i am running in full-screen mode that is not the problem.
As i said when i am looking at my desktop or playing another game the screen is where it's supposed to be and no sides or edges are "pushed" off my tv.
Any help is appreciated !