Broken Callouts in MKMapView

[Lanturn]

I'm trying to use a reverse geocoded address in the subtitle of a MKPinAnnotationView but the callout breaks as the subtitle is updated mid-animation.

However, in the main Maps app, I see the same thing happening but the animation is smooth and the callout doesn't break.
Any ideas?

Screen shot 2010-07-09 at PM 11.50.37.jpg

[saphroi]

Same problem here, anyone have a fix? Seems like a iOS4 related defect. Not happening in iOS5. I don't wanna roll my own callout feature, but I may have to if there's no easy workaround. Surprised no one else came across this problem.