MKMapView ignores update of centerOffset in iOS 4

Question

I previously created a custom callout bubble as a subview to the MKAnnotationView because the built in callout is so limited. This requires me to change to centerOffset of the MKAnnotationView when it is selected to account for the size of the callout bubble. This all worked perfectly before iOS 4 came out. Now, with iOS 4, it completely ignores my updating of the centerOffset property and therefore the pin and bubble appear to jump down and to the right (the top left corner of the callout bubble is now at the location where the pin point should be).

Does anyone know why this has changed in iOS 4? Is there something I can do to get the MKMapView to recognize the new centerOffset? Is this a bug that apple introduced?

Thanks for the help!