Event listeners

hi
I have this problem with mouse events
simply I added two listeners on a movieClip that simply contains two keyframes 1 and 2 the code is in external class file of the movieClip

addEventListener(MouseEvent.MOUSE_DOWN,downEvent);
addEventListener(MouseEvent.MOUSE_UP,upEvent);

private function downEvent(event:MouseEvent){
gotoAndStop(2);
}
private function upEvent(event:MouseEvent){
gotoAndStop(1);
}

but when it goes to frame 2 it does not answer the moseUp event and stucks in frame 2
please help me