[MerlinTwi]

InteractiveObject.setCapture убрали.
Можно так:

package {
	import flash.display.Sprite;
	import flash.events.*;

	dynamic public class Test extends Sprite {

		function Test() {
			buttonMode=true;
			addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
		}
		
		private function onMouseDown(e:Event):void {
			stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
		}
		private function onMouseUp(e:Event):void {
			stage.removeEventListener(MouseEvent.MOUSE_UP, onMouseUp);
			if (e.target==this) {
				trace("onRelease");
			} else {
				trace("onReleaseOutside");
			}
		}
		
	}
}