Sorry Michael, actual both of them are involved, I think...

Try this:

- draw a cube
- rotate it in top and front view using edit frame
- place a Cplane on one of cube's side
- delete the cube
- NOW, go to View>Cplane and push "Reset CPlane" button
- you can see that axis icon flicks a bit, but it still remains
in more or less original position until you manipulate viewport (pan, rotate, zoom..)

Petr