iPhone simulator only shows a black screen after launching the app

I am moving my 3.x app to use iOS4 features like background processing, fast-app switching. I have been able to get the app running fine. But now whenever I launch the app on the simulator, it just shows a black screen. The app launches, status in XCode changes to running but nothing shows up other than the black screen.

The app runs fine on a device so I know there's nothing wrong with the code. Any idea what coul开发者_如何学God be happening? I have tried reinstalling the SDK but it did not make a difference.

And yes, I have the [window makeKeyAndVisible]; line in the code. So that is not the issue. I am using application:didFinishLaunchingWithOptions: to handle the app launch.

Thanks.

I'm moving my app from 3.x to 4.x and have the same issue. Sound system is launched (music and sounds play well), but entire screen is black. It happens on 4.x simulator and device, but on 3.1.3 device everything seems well.

UPDATE: Recently i have added some window manipulations after application init:

[window center];
[window makeKeyAndVisible];
[window becomeFirstResponder];

and now it's alive =)

Some features do not work in the simulator, I know that when you try to access the iPod library in your app the simulator will just hang like this (it was this way back in 3.1 at least). Make sure you aren't using a feature that the simulator doesn't support.