App Crashing using popViewControllerAnimated:YES - iphone

Question

I am trying to create a back button to return to the main menu of my app, what is happening now, is, once I press the back button, it shows the main menu, but then the app crashes out a second later.
The code I use for back button is;
- (void)backButtonPressed:(id)sender {
[self.navigationController popViewControllerAnimated:YES];
}
From the AppDelegate.m file
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
self.viewController = [[[MenuViewController alloc] initWithNibName:#"MenuViewController_iPhone" bundle:nil] autorelease];
} else {
self.viewController = [[[MenuViewController alloc] initWithNibName:#"MenuViewController_iPad" bundle:nil] autorelease];
}
navigationController = [[myNavigationViewController alloc] initWithRootViewController:self.viewController];
navigationController.navigationBarHidden = YES;
self.window.rootViewController = navigationController;
[self.window makeKeyAndVisible];
return YES;
}
I cannot see where I am going wrong? It seems to call the right screen, yet crashes straight after?
EDIT - Here is MenuViewController.m file;
#import "MenuViewController.h"
#import "MagicAppDelegate.h"
#import "MagicViewController.h"
#interface MenuViewController ()
#end
#implementation MenuViewController
- (void)viewDidLoad
{
self.view.frame = [[UIScreen mainScreen] bounds];
[super viewDidLoad];
// [self initLoad];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(IBAction)onStart:(id)sender
{
MagicViewController* viewController;
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)
viewController = [[MagicViewController alloc] initWithNibName:#"MagicViewController_iPhone" bundle:[NSBundle mainBundle]];
else
viewController = [[MagicViewController alloc] initWithNibName:#"MagicViewController_iPad" bundle:[NSBundle mainBundle]];
[self.navigationController pushViewController:viewController animated:YES];
[viewController release];
}
- (void)dealloc {
[super dealloc];
}
#end

Answer 1

Please use below code,do u want go mainmenuview controller.
[self.navigationController popToRootViewControllerAnimated:YES];

Answer 2

Actually, I don't understand your code: In the statement navigationController = [[myNavigationViewController alloc] initWithRootViewController:self.viewController]; you are sending an alloc to something that seems to be the instance of class UINavigationController, but alloc is a class method. I therefore assume myNavigationViewController is a subclass of UINavigationController (but then is should start with a capital letter).
The new instance returned is then assigned directly, i.e. without using a setter method, to variable navigationController. It is therefore not retained. If your statement returns an autorelease object, it will thus be released as soon as the program returns to the main event loop.
Try thus to use thus a setter method, i.e. self.navigationController = [[myNavigationViewController alloc] initWithRootViewController:self.viewController];