title: self.navigationController.navigationBar.hidden = TRUE does not work on one UIViewController
body: <p>In my app I have at least a dozen <code>UIViewController</code>, some of them show navigation bar, some of them don't.  Everything works fine on all but one controllers.</p>
  
  <p>I navigate to this screen from another one that does not have the nav bar shown. On this one, I need the nav bar shown, so in my <code>viewWillAppear</code> I have this code:</p>
  
  <pre><code>[self.navigationController setNavigationBarHidden:NO animated:YES];
  </code></pre>
  
  <p>When I step through the code with a debugger, I go through this line, however it's just ignored and the nav bar is not shown.  This appears to be a problem on both the simulator and an actual device (iPhone 4S with iOS 5.1.1).</p>
  
  <p>What am I missing here?</p>