Application.LoadLevelAsync ... loading screen is freezing

Hello!

At the moment I'm working on loading screens for my game. I use the Application.LoadLevelAsync from http://docs.unity3d.com/Documentation/ScriptReference/Application.LoadLevelAsync.html

I have a mainmenu in my game. When I click on 'Start' a new Scene is loading which should be the loading screen. On the loading screen der is a little animation and in the background the mainscene is loading with the code from the link above.

The loading works fine but the loading screen is frozen .... the animation too.

I don't know why it doesn't work ... hope you understand what I mean.