I have a tab bar application in Xcode 4.3 and I'm trying to insert a login screen before the tabbar is shown. The app works OK if `presentModalViewController` has `animated:YES`but if it is without animation the view is not showing.

```
@synthesize window = _window;

@synthesize tabBarController = _tabBarController;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    UIViewController *viewController1 = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
    UIViewController *viewController2 = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];

    self.tabBarController = [[UITabBarController alloc] init];
    self.tabBarController.viewControllers = [NSArray arrayWithObjects:viewController1, viewController2, nil];
    self.window.rootViewController = self.tabBarController;

    LogInViewController *logViewController = [[LogInViewController alloc] initWithNibName:@"LogInViewController" bundle:nil];
    [self.window addSubview:_tabBarController.view];

    [self.tabBarController presentModalViewController:logViewController animated:YES];
    //This wont work
    //[self.tabBarController presentModalViewController:logViewController animated:NO];

    [self.window makeKeyAndVisible];
    return YES;

}

-(void)loginDone{

    NSLog(@"back to the app delegate");
   [self.tabBarController dismissModalViewControllerAnimated:YES];

}

```

1. Is this the right way to do it?
2. Why wont the code work with `animated:NO` ?
3. I also get this on output `Unbalanced calls to begin/end appearance transitions for <UITabBarController: 0x689d350>`.