Maps not working in IOS 4.2

I made one app in IOS4.0 which is working fine. but now i upgraded to IOS 4.2, and now the maps annotations are not showing. But its working absolutely fine on IOS 4.0.

the breakpoint is not coming to the third line of code given below i.e. "MKPinAnnotationView *view;".

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <M开发者_如何转开发KAnnotation>) annotation
{
    if ([annotation isKindOfClass:[MKUserLocation class]])
        return nil;

    MKPinAnnotationView *view;

Please help. Thanks in advance.

Why you are using these lines of code in Annotation

if ([annotation isKindOfClass:[MKUserLocation class]])

    return nil;

Your breakpoint is not coming to the third line just because it simply return by nil