my cursor change if I'm going out of the window

I've created a second cursor named "viseur" that is visible only on a particular scene.

I've called it in my Engine class like that :

        viseur = new Viseur(stage); stage.addChild(viseur); viseur.visible = false;

So it's not visible unless the player goes to the particular scene "room3"

var isMap:Boolean = thisBack == "room3"; if (isMap) { viseur.visible = true;

But, if the player use Alt+Tab during the game in order to go back to the desktop and come back to the game, "visor" is visible ! Even if he's not in room 3 ?

Do you know what could cause this ? (to resume : if the cursor leave the game windows and come back, the new cursor "viseur" is visible even so it is no suppose to be)

Thank you for your help,