i have this xml which contains google maps v2:
If you are running your code for API level <11, use FragmentActivity
instead of extending Activity
and in XML, use "com.google.android.gms.maps.SupportMapFragment"
Your problem is below 3.0 versions not support Fragments, but you are using.
Solution:
1)set your minimumSDk="11" and run into 3.0 or above versions of device.
or
2)Use SupportMapFragment instead of MapFragment and Add Support Library
into your project.
(Right click on your project -> Android Tools -> click Add Support Library)