Error #2025: The supplied DisplayObject must be a child of the caller

1

Hi,

doesnt seem to be able to find solution for this error, Error #2025: The supplied DisplayObject must be a child of the caller.

Help is very much appreciated. =) and Pardon me from my messy code.

import caurina.transitions.*;
stop();
// set Boonlean to check if flipping is over.
var endFlipping:Boolean=false;
var flipCounts:Number=0;
//
addEventListener(Event.ENTER_FRAME, languageAndMenu);

function languageAndMenu(event:Event):void {
    if (flipCounts=="0") {
        if (preloaderContainer_mc.rotationY>90&&preloaderContainer_mc.rotationY<270) {
            languageBar= new Mc_LanguageBar();
            preloaderContainer_mc.addChild(languageBar);
            languageBar.y = -(languageBar.height/2);
            languageBar.english_btn.addEventListener(MouseEvent.CLICK, languageBarButton);
        }
    } else if (flipCounts=="1") {
        if (preloaderContainer_mc.rotationY>90&&preloaderContainer_mc.rotationY<270) {
            removeChild(languageBar);
        }
    }


    if (preloaderContainer_mc.rotationY>=180) {
        endFlipping=true;
    } else if (preloaderContainer_mc.rotationY>=360) {
        endFlipping=true;
        preloaderContainer_mc.rotationY=0;

    }
    if (endFlipping==true) {
        endFlipping=false;

        if (flipCounts=="0") {
            removeEventListener(Event.ENTER_FRAME, languageAndMenu);
        } else if (flipCounts=="1") {
            removeEventListener(Event.ENTER_FRAME, languageAndMenu);
        }
        flipCounts++;
     }
}

function languageBarButton(event:MouseEvent) {
    if (preloaderContainer_mc.rotationY>=359) {

        preloaderContainer_mc.rotationY=0;

    }
    Tweener.addTween(preloaderContainer_mc, {rotationY:preloaderContainer_mc.rotationY+180, time:2});
    addEventListener(Event.ENTER_FRAME, languageAndMenu);
}