Fullscreen resize issue

I have this code for a full screen flash site and I just noticed that after progressing into the animation, when you resize the browser window the code tells all the mc’s to go back to their original positions on the stage, is there a work around for this?

Stage.scaleMode = "noScale";
Stage.align = "TL";
import caurina.transitions.Tweener;
function reposition() {
        var mainbg = _root.mainBG;
  nPos = getNewPosition(mainbg);
        mainbg._x = nPos.x;
        mainbg._y = nPos.y;
  Tweener.addTween(btn01, {_x:Stage.width-85, _y:Stage.height-25, time:0.5, transition:"easeOutQuad"});
  Tweener.addTween(btn02, {_x:Stage.width-791, _y:Stage.height-133, time:0.5, transition:"easeOutQuad"});
  Tweener.addTween(nav, {_x:Stage.width/2, _y:Stage.height/2, time:0.5, transition:"easeOutQuad"});
function getNewPosition(mc) {
        var newX = Math.floor((Stage.width - mc._width) / 2);
        var newY = Math.floor((Stage.height - mc._height) / 2);
        return {x:newX, y:newY};
btn01.onPress = function() {
 Tweener.addTween(nav, {_x:0, _y:0, time:0.5, transition:"easeOutQuad"});
btn02.onPress = function() {
 Tweener.addTween(nav, {_x:Stage.width - 500, _y:Stage.height - 500, time:0.5, transition:"easeOutQuad"});