NullReferenceExeption: Object reference not set to an instance of an object.

Hi, I was just opening up Unity today and i got a message about an update, but since my internet was down at the moment, I selected No. When I got to my project I wanted to open up the Game View, but when i pressed space, only a small area of Unity got covered with that window. I perssed Space again, and now all the windows are gone! I can still press Window at the top and choose one, but I can't attach them anywhere. All I see is an error saying: "NullReferenceExeption: Object reference not set to an instance of an object. UnityEditor.MaximizedHostView.OnGUI () (at C:/BuildAgent/workblablabla)"