quiz game with Countdown Timer AS3

hi

i created quiz game with score and limit time for every question.

i don't get any error but when i reach question 4 the timer get crazy and play 10, 7, 4, 1...

this is the code of question 4

please help

stop();

scoretext.text = score.toString();

q4.visible = true;

q4a.visible = true;

q4b.visible = true;

q4c.visible = true;

wrong.visible = false;

right.visible = false;

timeIsUp.visible = false;

nextbutton.visible = false;

q4a.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndStopAtFrame_204);

function fl_ClickToGoToAndStopAtFrame_204(event:MouseEvent):void

{

q4.visible = true;

q4a.visible = true;

q4b.visible = true;

q4c.visible = true;

wrong.visible = true;

right.visible = false;

nextbutton.visible = true;

gameTimer.removeEventListener(TimerEvent.TIMER, countDown_4);

}

q4b.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndStopAtFrame_304);

function fl_ClickToGoToAndStopAtFrame_304(event:MouseEvent):void

{

q4.visible = true;

q4a.visible = true;

q4b.visible = true;

q4c.visible = true;

wrong.visible = true;

right.visible = false;

nextbutton.visible = true;

gameTimer.removeEventListener(TimerEvent.TIMER, countDown_4);

}

q4c.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndStopAtFrame_404);

function fl_ClickToGoToAndStopAtFrame_404(event:MouseEvent):void

{

q4.visible = true;

q4a.visible = true;

q4b.visible = true;

q4c.visible = true;

wrong.visible = false;

right.visible = true;

nextbutton.visible = true;

score = score +5;

gameTimer.removeEventListener(TimerEvent.TIMER, countDown_4);

}

timeleft=10;

timerbox.text=timeleft.toString();

gameTimer = new Timer (1000,0);

gameTimer.addEventListener(TimerEvent.TIMER, countDown_4);

function countDown_4 (e:TimerEvent): void {

            timeleft--;

            timerbox.text= timeleft.toString();

            if(timeleft<1){

                        timeIsUp.visible = true;

                        nextbutton.visible = true;

                        gameTimer.removeEventListener(TimerEvent.TIMER, countDown_4);

            }

}

gameTimer.start();

nextbutton.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndStopAtFrame_504);

function fl_ClickToGoToAndStopAtFrame_504(event:MouseEvent):void

{

            gotoAndStop(6);

}