ActionScript 3.0 :: Tweener Causing Stage To Jump Around

The .swf I am having trouble with is embedded on the front of my home page [URL]. I am trying to make it so when the back button is pressed it causes the four buttons to move 200px left and when the forward button is hit right 200px. Here is the code for the back button, forward is identical minus the - sign...

back.buttonMode = true;// creates the hand cursor
back.addEventListener("click", onClick3);
function onClick3 (obj:Object){
back.buttonMode = false;// creates the hand cursor
Tweener.addTween (homebutton, {alpha:1, time:3, x:x-=200});
Tweener.addTween (button2, {alpha:1, time:3, x:x-=200});
Tweener.addTween (button3, {alpha:1, time:3, x:x-=200});
Tweener.addTween (button4, {alpha:1, time:3, x:x-=200});
}