[flexcomponents] TitleWindow Problem

[loc_tran106]

Hello All,

I have a problem that is bugging me big time.  I'm writing a new
component for one of my applications which extends a titlewindow.

Each titlewindow contains a tabnavigator, and I programically
add/remove tabs to the tabnav.  However, everytime I do that, the
titlewindow itself moves to the top of the screen and I have no clue why.

Can someone help explain to me what causes this problem? when you
click on "Add 3 more tabs" button?

TIA.

-Loc

Main Application:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; >
        <mx:Script>
                <![CDATA[
                        import mx.managers.PopUpManager;
                        
                        private var tmpWindow:windowBug;
                        
                        private function PopMeUp():void {
                                tmpWindow =
windowBug(PopUpManager.createPopUp(mainCanvas,windowBug,false));
                                PopUpManager.centerPopUp(tmpWindow);
                        }
                ]]>
        </mx:Script>
        <mx:Canvas width="100%" height="100%" id="mainCanvas" >
                <mx:Button click="PopMeUp()" label="Click Here" />
        </mx:Canvas>
</mx:Application>

Component: (windowBug.mxml)

<?xml version="1.0" encoding="utf-8"?>
<mx:TitleWindow xmlns:mx="http://www.adobe.com/2006/mxml";
layout="vertical" width="400" height="300" title="Bug Test">
        <mx:Script>
                <![CDATA[
                        import mx.controls.Label;
                        import mx.containers.VBox;
                        import mx.events.*;
                        
                        private function addMore():void {
                                var newVBox:VBox;
                                var newLabel:Label;
                                for (y=0; y<3; y++) {
                                        newVBox = new VBox;
                                        newVBox.label= "Added " + y;
                                        newLabel = new Label;
                                        newLabel.text = "Hello " + 
newVBox.label;
                                        newVBox.addChild(newLabel);
                                        
newVBox.addEventListener("doSomething",doSomethingNow);
                                        nav.addChild(newVBox);
                                }
                        }
                        
                        private function doSomethingNow(event:Event):void {
                                trace ('nada');
                        }
                        
                ]]>
        </mx:Script>
        <mx:Button click="addMore()" label="Add 3 More Tabs" />
        <mx:TabNavigator id="nav">
                <mx:VBox label="1" >
                        <mx:Label text="Hello 1" />
                </mx:VBox>
                <mx:VBox label="2" >
                        <mx:Label text="Hello 2" />
                </mx:VBox>
                <mx:VBox label="3" >
                        <mx:Label text="Hello 3" />
                </mx:VBox>
                <mx:VBox label="4" >
                        <mx:Label text="Hello 4" />
                </mx:VBox>                                              
        </mx:TabNavigator>
</mx:TitleWindow>