When you present a modal view controller it does not use any existing navigation controllers or navigation bars. If all you want is to display a navigation bar, you need to add the navigation bar as a subview of your modal view and present it as you’re doing.
If you want to present a modal view controller with navigation functionality, you need to present a modal navigation controller containing your detail view controller instead, like so:
SettingsCreateAccount *detailViewController = [[SettingsCreateAccount alloc] initWithStyle:UITableViewStyleGrouped];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:detailViewController];
[detailViewController release];
navController.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:navController animated:YES];
[navController release];
Your modal controller will manage its own navigation stack.