Weird Behavior While Switching Views

[sam-stersing]

Hi

I've integrated your MapKit in one of my projects, I did all the steps. But there is a problem.
Here I'm using a NSToolbar and switching between the views. whenever I'm in my map page if I switch in another page and then switch back to the map page, the map is drew under the MKMapView and MKMapView is white but I can navigate in map by dragging mouse in the white area.

Regards