Was wondering if anyone else has this issue....

Every time I start up CC3, the viewport is cropped. I have to keep minimising, maximising and dragging the viewport round until it eventually pops back into shape.
I update the graphics card drivers religiously. (Last updated less than 24hrs ago!)
I didnt know if I've accidentally hit a shortcut key or something to maybe put it in 'narrow mode' on start up?
At first it didnt bother me, but now it's really starting to become quite annoying...

Any help greatly appreciated!
Cheers