title: Presenting modal view occasionally hides the navigation bar
body: <p>I've come across this twice now.</p>
  
  <p>Sometimes using the following line of code:    </p>
  
  <pre><code>[self.navigationController presentModalViewController:aViewController animated:YES];
  </code></pre>
  
  <p>displays the view, but the navigation bar is then hidden.</p>
  
  <p>I can write:</p>
  
  <pre><code>[self.navigationController setNavigationBarHidden:NO];
  </code></pre>
  
  <p>to my hearts content, everywhere I can think of with no effect.</p>
  
  <p>Has anyone ran into this?</p>
  
  <p>Am I doing something silly?</p>