title: backButton of NavigationController don't appear
body: <p>I have already post this question but this time I post code. So I have a uiviewController, and in the viewDidLoad of this viewController I hide the backButton of the navigationController. After that, I push a new uiviewcontroller, and I set the backbutton to visible in the viewDidLoad, but the backbutton is still hidden...</p>
  
  <p>Implementation of the first uiviewcontroller</p>
  
  <pre><code>- (void)viewDidLoad {
      [super viewDidLoad];
  
      self.navigationItem.title = @"page2page2page2page2page2";
  
      self.navigationItem.hidesBackButton = TRUE;
  }
  
  -(IBAction)click
  {
      page3 *controller = [[page3 alloc] init];
  
      [self.navigationController pushViewController:controller animated:YES];
  
      [page3 release];
  }
  </code></pre>
  
  <p>Implementation of the  page 3</p>
  
  <pre><code>- (void)viewDidLoad {
      [super viewDidLoad];
  
      self.navigationItem.title = @"page3";
      self.navigationItem.hidesBackButton = FALSE;
  
  }
  </code></pre>
  
  <p>and the page3 has no backbutton, but the space is created for the button, because the tile "page 3" is on the right and not in the center... all this happen with the ios 4.2</p>
  
  <p>thx</p>