iphone App screen getting stuck on iOS 5

I am working on iphone application, my app is working on xcode 4.0 and later versions but when I try to test my app on xcode 4.2-iO开发者_如何学PythonS 5, app screen stuck inconsistently and cannot debug.

Place breakpoints in your App delegate and in view controller's viewWillAppear that you add to window.Look at stack trace.