Problem: the push notification dialog only appears once for your debug application. It doesn't matter that you remove the app and reinstalled it - it won't appear again. This kind of behavior is dangerous for developers because it means it's impossible for you to test the push notification registration step reliably - it might have worked last week but stopped working this week, and you just wouldn't know.
Apple has a technical note dealing with this behavior. What an app developer can do in this case is to uninstall the app and adjust his development phone's clock to 1 day later. If he reinstalls the app after this, the push notification dialog will be allowed to appear again.
But... there's always a better way. It requires jailbreaking your iPhone but who doesn't? :)