This is not a V4 vs V5 thing. In my opinion the only explanation is that when you see this flopped camera movement, you’ve got the camera upside down. When you see it, turn on the camera for the perspective viewport (Camera show). With the camera widget on, when you look at it in one of the other viewports, you will see a line that runs from the camera target to the edge of the camera frame, that should point up. When you are experiencing flopped camera movement, my guess is that it will be pointing down.
Is it possible that between your version of V4 and V5, you have got a different setting for Rhino Options -> View -> Rotate around wold axes / Rotate relative to view?