We recently tested our application against android API level 14 and 15. We started development targeting minimal SKD Version 8 and excluding tablets (3.x).
With 2.x ever
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 300000, 500, locationListener);
In your code use this LocationManager.NETWORK_PROVIDER
when you testing that make sure that the network you are using like WIFI is available or you are inserted sim card in your device and network is available on it.
You may also test using LocationManager.GPS_PROVIDER
but make sure before use that GPS is ON of device
I think this may be an issue with the Android Emulator at present.
See http://code.google.com/p/android/issues/detail?id=21237