title: Unbalanced calls to begin/end appearance transitions for <UITabBarController: 0x197870>
body: <p>I read SO about another user encountering similar <a href="https://stackoverflow.com/questions/6809593/unbalanced-calls-to-begin-end-appearance-transitions-for-firstviewcontroller-0">error</a>, but this error is in different case.</p>
  
  <p>I received this message when I added a View Controller initially:</p>
  
  <pre><code>Unbalanced calls to begin/end appearance transitions for 
  &lt;UITabBarController: 0x197870&gt;
  </code></pre>
  
  <p>The structure of the app is as follow:</p>
  
  <p>I got a 5-tab TabBarController linked to 5 View Controllers. In the initial showing tab, I call out a new View Controller to overlay as an introduction of the app.</p>
  
  <p>I use this code to call the introduction view controller:</p>
  
  <pre><code>IntroVC *vc = [[IntroVC alloc] init];
  [self presentModalViewController:vc animated:YES];
  [vc release]; 
  </code></pre>
  
  <p>After this <code>IntroVC</code> view controller shows up, the above error shows. </p>
  
  <p>p.s. I am using xCode 4.2 &amp; iOS 5.0 SDK, developing iOS 4.3 app.</p>