Question

   - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:    (UIControl *)control{
        NSLog(@"Disclosure button pressed");
        DetailView *tmpView = [[DetailView alloc]initWithNibName:@"DetailView" bundle:nil];
        self.detailViewController = tmpView;

        [self.navigationController pushViewController:self.detailViewController animated:YES];
        //[self.view addSubview:detailViewController.view];
        [tmpView release];
    }

Answer 1

Are you sure the navigation controller exists in current view controller from where you click on the map annotation? Make sure self.navigationController is not nil.