So, I have this view hierarchy in my app:

UIWindow
UIViewController
UITabBarController -> 4 UINavigationController

I know that a UITabBarController is designed to be the topmost view in an app, however this isn't possible in my case. However, the problem that I have is that ~20 of the lower pixels aren't responsive for touches so that the UITabBarController doesn't trigger the tab changes correctly. This happens on an actual device (iPad and iPhone 3G).

My question is, are there any obvious reasons why this could happen? I add the UITabBarController like this as subview to my UIViewController view:

- (void)viewDidLoad 
{
    [super viewDidLoad];
    [self.view addSubview:controller.view]; // Controller is the UITabBarController
}

I didn't set the UITabBarController's delegate.