I've noticed that the viewport camera goes nuts after some specific mouse action.
1. Put the mouse at very close to the border of the viewport window
2. Press and hold the right mouse button (as you would do when changing the camera direction)
3. Now quickly move the mouse outside the viewport.. I mean, very quickly.
4. Then move your mouse back into the viewport
Your mouse will become invisible and your viewport camera will be out of control.
Your mouse will only be visible when it is outside the viewport.
The only remedie i found was to right click in the viewport. But I still think this bug deserves a fix.