программа получила сигнал "EXC_BAD_ACCESS"

Когда я управляю этим после кода, это дает выше ошибки

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{


   self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

    [self.window makeKeyAndVisible];

    self.viewController = [[ViewController alloc] initWithNibName:nil bundle:nil];
    self.firstViewController=[[FirstViewController alloc]initWithNibName:nil bundle:nil];
    UINavigationController *localNavigationController=[[UINavigationController alloc]initWithRootViewController:self.viewController];
    self.navigationController=localNavigationController;
    [localNavigationController release];
    UINavigationController *localFistNavigationController=[[UINavigationController alloc]initWithRootViewController:self.firstViewController];
    self.firstNavigationController=localFistNavigationController;
    [localNavigationController release];
   NSArray *twoBars=[[NSArray alloc]initWithObjects:self.navigationController,self.firstNavigationController, nil];
    UITabBarController *localTAbBarController =[[UITabBarController alloc]init];
    [localTAbBarController setViewControllers:twoBars];
    self.tabBarController=localTAbBarController;
    [localTAbBarController release];
    [self.window addSubview:self.tabBarController.view];

        return YES;
}

если я управляю следующим кодом, он бежит хорошо

self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
         [self.window makeKeyAndVisible];

    self.viewController = [[ViewController alloc] initWithNibName:nil bundle:nil];
    self.firstViewController = [[FirstViewController alloc] initWithNibName:nil bundle:nil];

    self.navigationController = [[UINavigationController alloc]
                                 initWithRootViewController:self.viewController];

    self.firstNavigationController=[[UINavigationController alloc]initWithRootViewController:self.firstViewController];
    NSArray *twoBars=[[NSArray alloc]initWithObjects:self.navigationController,self.firstNavigationController, nil];

    self.tabBarController=[[UITabBarController alloc]init];
    [self.tabBarController setViewControllers:twoBars];

       [self.window addSubview:self.tabBarController.view];



    return YES;

i not understood what is the difference between these. in first one i just created local variables & assigned those to properties. in later one directly used the properties. why it is giving the error- program recieved signal "EXC_BAD_ACCESS"