IOS6: supportedInterfaceOrientations not working (is invoked but the interface still rotates)

This is long after the fact, but just in case anybody comes along who isn't using a navigation controller and/or doesn't wish to use undocumented methods:

UIViewController *c = [[UIViewController alloc]init];
[self presentModalViewController:c animated:NO];
[self dismissModalViewControllerAnimated:NO];
[c release];

It is sufficient to present and dismiss a vanilla view controller.

Obviously you'll still need to confirm or deny the orientation in your override of shouldAutorotateToInterfaceOrientation. But this will cause shouldAutorotate... to be called again by the system.

I had the same problem and found a solution that works for me. To make it work, it is not sufficient to implement - (NSUInteger)supportedInterfaceOrientations in your UINavigationController. You also need to implement this method in your controller #3, which is the first one to be portrait-only after popping controller #4. So, I have the following code in my UINavigationController:

- (BOOL)shouldAutorotate
{
    return YES;
}

- (NSUInteger)supportedInterfaceOrientations
{
    if (self.isLandscapeOK) {
        // for iPhone, you could also return UIInterfaceOrientationMaskAllButUpsideDown
        return UIInterfaceOrientationMaskAll;
    }
    return UIInterfaceOrientationMaskPortrait;
}

In view controller #3, add the following:

- (NSUInteger)supportedInterfaceOrientations
{
    return UIInterfaceOrientationMaskPortrait;
}

You don't need to add anything to your view controllers #1, #2, and #4. This works for me, I hope it will help you.