http://www.adobe.com/livedocs/flash/...l#displayState
Full-screen mode is initiated in response to a
mouse click or key press by the user; the movie cannot change Stage.displayState without user input. While Flash Player is in full-screen mode, all keyboard input is disabled (except keyboard shortcuts that take the user out of full-screen mode). A Flash Player dialog box appears over the movie when users enter full-screen mode to inform the users they are in full-screen mode and that they can press the Escape key to end full-screen mode.