[Solved] Problem with .obj model and camera update

I have a strange problem that I've never had before basically now I have got a .obj model to load I can't call cam.update() after setting a new location or direction for the camera without the screen going black, but after you move the mouse the scene comes back. I guess theres some update I'm not calling any help would be greatly appreciated.

it was a problem to do with not normalizing the camera so after normalizing the camera it fixed the problem.