I have this problem with my camera in the scene. As I set render border and the turned it off a gray area stayed behind that cuts off any object from the perspective. Even after moving the camera. Its not a problem wit clipping was looking into that already. I already moved all the objects into a new blender file just curious if this is a bug or just some setting I dont know about. :o
Posting your blend file can help us in finding what actually is the problem.