I am running same app in iOS6 and iOS7 which has NavigationBar.It runs well on iOS6, but in iOS7, all view is little bit up like it is not considering the Navigation bar at all.
At the time of this answer, iOS 7 was still under NDA, so it was not possible to write the actual solution. To help anyway, I've posted a helping link available only for registered developers.
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Read the iOS 7 Transition Guide. Its section 'Updating the UI' explains how to fix your problem.