I\'ve come across this twice now.
Sometimes using the following line of code:
[self.navigationController presentModalViewController:aViewControll
If there is a navigation controller active, then you should just use
[self.navigationController pushViewControllerAnimated:how];
to slide another view controller in, while giving yourself and the user into a consistent user interface complete with 'automatic' back button support.
Once a navigation controller is in use, presenting a modal view controller should only be done to enlarge the usable area on the screen. And then, you should really use a fancy animation to let the user know that you are stepping away from the "task" or "steps" that the navigation controller was embodying.