(FP Bug?) - Mc's/Sprite's events triggered when mouse leaves SWF area

Question

Hi guys,
I wonder if somebody had a similar problem and can help out. I have a button on y=0 (may be either Movieclip or Sprite) with two events: ROLL_OVER and ROLL_OUT. Now when the mouse pointer leaves the SWF area, both of these events get triggered, even if the button is not hovered at all. There is no MOUSE_LEAVE event defined nor anything like that (see the code below). I realized that changing the y position of the button helps, strangely small numbers don't - if I set y=1 the bug still occurs, but y=20 solves the problem. What the hell? This happens only in Firefox on Mac, Safari seems to work alright. (FF 5.0.1 and 6 tested, on OSX 10.6.8 and 10.7)
I uploaded a video to youtube in case somebody would be interested of seeing this from Windows (where I assume this doesn't happen, but cannot test at the moment - please leave feedback if you could - http://www.youtube.com/watch?v=YKWl50v_MIo - first 10 seconds are kinda crappy, sorry)
Is this a Flash Player bug or am I missing something really badly here? Thanks!
package {
    import flash.display.Sprite;
    import flash.display.Stage;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.display.MovieClip;
    import flash.text.TextField;
    public class Main extends Sprite {
        private var field:TextField;
        public function Main() {
            stage.align = StageAlign.TOP_LEFT;
            stage.scaleMode = StageScaleMode.NO_SCALE;
            //Set up the textfield
            field = new TextField();
            field.x = 200;
            field.y = 200;
            field.border = true;
            field.width = 200;
            field.height = 100;
            field.wordWrap = true;
            addChild(field);
            //Create and set up the MovieClip or Sprite - the MovieClip/Sprite must have content,
            //cannot be empty, otherwise the bug doesn't appear!
            var b:MovieClip = new MovieClip();
            b.graphics.beginFill(0xCCCCCC);
            b.graphics.drawRect(0, 0, 50, 50);
            b.graphics.endFill();
            addChild(b);
            b.y = 0;
            b.addEventListener(MouseEvent.ROLL_OVER, rollOverHandler);
            b.addEventListener(MouseEvent.ROLL_OUT, rollOutHandler);
        private function rollOverHandler(e:MouseEvent):void {
            field.appendText("Over"+new Date().getTime()+"\n");
            field.scrollV = field.maxScrollV;
        private function rollOutHandler(e:MouseEvent):void {
            field.appendText("Out"+new Date().getTime()+"\n");
            field.scrollV = field.maxScrollV;

Answer 1

Yep, strange thing. I filed a report so feel free to vote. https://bugbase.adobe.com/index.cfm?event=bug&id=2944625