title: crash after UIAlertViewDelegate's clickedButtonAtIndex with message [MPMoviePlayerViewController isKindOfClass:]: message sent to deallocated instance
body: <p>I just want to dismiss <code>UIAlertView</code> but I can't with a strange bug for some days...</p>
  
  <p>After tapping cancel button on <code>UIAlertView</code>, Codes below works. </p>
  
  <pre><code>- (void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex 
  {
      [alertView dismissWithClickedButtonIndex:buttonIndex animated:YES];
  }
  </code></pre>
  
  <p>But After passing these lines, it makes crash with message below:</p>
  
  <pre><code>[MPMoviePlayerViewController isKindOfClass:]: message sent to deallocated instance 0x27f590
  </code></pre>
  
  <p>On the same view, I embed </p>
  
  <pre><code>MPMoviePlayerViewController.moviePlayer.view
  [self.view addSubview:vc.moviePlayer.view];
  </code></pre>
  
  <p>Does Anybody know what happend?
  I use ARC, iOS5.1. If you need more information, I do add them.</p>
  
  <p>Thank you in advance.</p>
  
  <p><strong>more info:</strong></p>
  
  <p>I set breakpoints on all methods in my code.
  And I made sure that it crashes after <code>clickedButtonAtIndex</code>...</p>
  
  <p>codes for calling UIAlertView show are</p>
  
  <pre><code>-(void)applicationDidBecomeActive:(NSNotification *)notification
  {
      self.alert = hoge; // set delegate = self
      [self.alert show];
  }
  </code></pre>
  
  <p>after calling them, <code>viewDidAppear</code>'s called.
  There are codes for enbedding <code>vc.moviePlayer.view</code> like</p>
  
  <pre><code>MPMoviePlayerViewController *vc;
  vc = [[MPMoviePlayerViewController alloc] initWithContentURL:hogeURL];
  
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(finishPreload:)
                                               name:MPMediaPlaybackIsPreparedToPlayDidChangeNotification
                                             object:vc];
  
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(finishPlayback:)
                                               name:MPMoviePlayerPlaybackDidFinishNotification
                                             object:vc];
  
  vc.view.frame = CGRectMake( 0, 0, 320, 440);
  
  vc.moviePlayer.allowsAirPlay = YES;
  vc.moviePlayer.shouldAutoplay = NO;
  vc.moviePlayer.controlStyle = MPMovieControlStyleEmbedded;
  vc.moviePlayer.useApplicationAudioSession = NO;
  
  [vc.moviePlayer.view setTag:310];
  
  [self.view addSubview:vc.moviePlayer.view];
  </code></pre>
  
  <p>My app has 3 tabs, 2 of them's embed <code>MPMoviePlayerViewController.moviePlayer.view</code>. Method called in the other tabs's controller are <code>viewWillDisappear</code> and <code>viewDidDisappear</code> only.</p>