Android: Bottom of Google Maps gets black inside the application

I have one Map on my main activity and It works fine. Recently I added another small map view on one of my sub activities using the same google map key. Now when I press back after looking at the map on sub activity, it returns to the main view and bottom of the map on main activity turns black. See the attached image.

Is there anyone who has faced this problem and know why sometimes bottom of map turns balc开发者_StackOverflow中文版k?

---

You can only have 1 map activity per process.

http://code.google.com/android/add-ons/google-apis/reference/com/google/android/maps/MapActivity.html