As3 button problem

On my project I put a button on the frame2 that leads to frame50 where there is a movieclip on this frame.It works very well up to this point but when I closed the clip and go back to frame2 my project is not going forward with arrow buttons but going back with back button.If anyone help, I will appreciate it very much.

My arrow button codes like this:

next_btn.addEventListener(MouseEvent.MOUSE_DOWN, nextClick);
function nextClick(event:MouseEvent):void{



back_btn.addEventListener(MouseEvent.MOUSE_DOWN, backClick);
function backClick(event:MouseEvent):void{



my close button codes are as follows:
close_btn.addEventListener(MouseEvent.MOUSE_DOWN, closeClick);
function closeClick(event:MouseEvent):void{