Сбой активности из-за MapView

У меня возникли проблемы с отображением основной активности в Android. Проблемы начались, когда Activity расширяет MapView (я не знаю почему). LogCat показывает некоторые ошибки, но я не знаю, что они означают. Вот LogCat:

03-07 05:42:56.859: D/AndroidRuntime(15357): Shutting down VM
03-07 05:42:56.859: W/dalvikvm(15357): threadid=1: thread exiting with uncaught exception (group=0x40018578)
03-07 05:42:56.859: E/AndroidRuntime(15357): FATAL EXCEPTION: main
03-07 05:42:56.859: E/AndroidRuntime(15357): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.geo.location/com.geo.location.GeoLocationActivity}: java.lang.IllegalArgumentException: listener==null
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.os.Looper.loop(Looper.java:130)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread.main(ActivityThread.java:3687)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at java.lang.reflect.Method.invokeNative(Native Method)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at java.lang.reflect.Method.invoke(Method.java:507)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at dalvik.system.NativeStart.main(Native Method)
03-07 05:42:56.859: E/AndroidRuntime(15357): Caused by: java.lang.IllegalArgumentException: listener==null
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.location.LocationManager.requestLocationUpdates(LocationManager.java:444)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at com.geo.location.GeoLocationActivity.onCreate(GeoLocationActivity.java:64)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-07 05:42:56.859: E/AndroidRuntime(15357):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
03-07 05:42:56.859: E/AndroidRuntime(15357):    ... 11 more

И это код приложения.

public class GeoLocationActivity extends MapActivity implements LocationListener {
    private TextView lblLatitud; 
    private TextView lblLongitud;
    private TextView lblPrecision;
    private TextView lblEstado;
    private TextView lblVelocidad;
    private DecimalFormat df;
    private MapView lblMapView; 
    private MapController mapController; 
    private LocationManager locManager;
    private LocationListener locListener;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        df = new DecimalFormat("#.########");
        lblLatitud = (TextView) findViewById(R.id.LblPosLatitud);
        lblLongitud = (TextView) findViewById(R.id.LblPosLongitud);
        lblPrecision = (TextView) findViewById(R.id.LblPosPrecision);
        lblVelocidad = (TextView) findViewById(R.id.LblV);
        lblEstado = (TextView) findViewById(R.id.textView8);
        lblPrecision = (TextView) findViewById(R.id.LblPosPrecision);
        lblMapView  = (MapView) findViewById(R.id.mapview);
        lblMapView.setBuiltInZoomControls(true);

        lblLatitud.setText("");
        lblLongitud.setText("");
        lblPrecision.setText("");
        lblVelocidad.setText("");
        lblEstado.setText("");
        lblPrecision.setText("");

        locManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
        //Obtenemos la última posición conocida
        Location loc = locManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        //Mostramos la última posición conocida
        mostrarPosicion(loc);
        locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locListener);

    }

    //Rellena los TextView de la Activity con la información básica de la posición
    private void mostrarPosicion(Location loc) {
        if(loc != null){
            lblLatitud.setText(String.valueOf(df.format(loc.getLatitude())));
            lblLongitud.setText(String.valueOf(df.format(loc.getLongitude())));
            lblPrecision.setText(String.valueOf(loc.getAccuracy())+ " metros");
            lblEstado.setText("GPS Ok");
            lblVelocidad.setText(String.valueOf(loc.getSpeed()*(3600/1000)) + "km/h <=> " + String.valueOf(loc.getSpeed()) + "m/s"); 
        }else{
            lblLatitud.setText("(sin_datos)");
            lblLongitud.setText("(sin_datos)");
            lblEstado.setText("(GPS no disponible)");
            lblPrecision.setText("(sin_datos)");
            lblVelocidad.setText("(sin_datos)");
        }
    }

    @Override
    protected boolean isRouteDisplayed() {
        return false;
    }

    //Añade un punto al array y muestra la posicion en el mapa
    protected void updateLocation(Location location) {
        GeoPoint point = new GeoPoint((int)(location.getLatitude() * 1E6), (int)(location.getLongitude() * 1E6));   
        mapController = lblMapView.getController();
        mapController.animateTo(point);
        mapController.setZoom(lblMapView.getMaxZoomLevel());    
        List<Overlay> mapOverlays = lblMapView.getOverlays();
        MiOverlay2 marker = new MiOverlay2(point, this);
        mapOverlays.add(marker);
        lblMapView.invalidate();
    }

    public void onLocationChanged(Location location) {
        lblEstado.setText("Gps Ok");
        mostrarPosicion(location);
        updateLocation(location);
    }
    public void onProviderDisabled(String provider){
        lblEstado.setText("No connection");
        Intent intent = new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
        startActivity(intent);
    }
    public void onProviderEnabled(String provider){
        lblEstado.setText("Gps Ok");
    }
    public void onStatusChanged(String provider, int status, Bundle extras){
        Log.i("", "Provider Status: " + status);
    }
}


 /***********************************************************************
 * CLASS:                                                               *
 * OVERLAY QUE PINTA LAS FLECHAS EN LUGAR DONDE ESTA SITUADO EL USUARIO *
 ***********************************************************************/
class MiOverlay extends Overlay { 
    GeoPoint punto; 
    Context ctxt; 

    public MiOverlay (GeoPoint punto, Context ctxt) {
        super();
        this.punto = punto;
        this.ctxt = ctxt; 
    }

    @Override
    public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) {
        super.draw(canvas, mapView, shadow);

       //se traduce el punto geo localizado a un punto en la pantalla
       Point scrnPoint = new Point();
       mapView.getProjection().toPixels(punto, scrnPoint);

       //se construye un bitmap a partir de la imagen
       Bitmap marker = BitmapFactory.decodeResource(ctxt.getResources() , R.drawable.arrow);

       //se dibuja la imagen del marker
       canvas.drawBitmap(marker,
               scrnPoint.x - marker.getWidth() / 2,
               scrnPoint.y - marker.getHeight(), 
               null);
       return true;
    }
} 

Как вы можете видеть, это очень простая программа, но я не могу решить эту проблему.