[flexcoders] RangeError

[Easy Flexing]

Hi All,

I am creating a multiple row tabs using Flex 2. Using 2 view stacks and a Vbox 
inside a container and using array as dataprovider to the view stacks. Once, a 
tab is selected, I remove all the children from the vbox and add my component 
into it. I created the same multiple row tab component using Flex 3 for another 
project and it works fine. But for some reason, it throws Range Error in Flex 2 
project.

This is what I am getting
RangeError: Error #2006: The supplied index is out of bounds.
    at flash.display::DisplayObjectContainer/getChildAt()
    at 
mx.core::Container/getChildAt()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\Container.as:2369]
    at 
mx.containers.utilityClasses::BoxLayout/measure()[C:\dev\flex_201_gmc\sdk\frameworks\mx\containers\utilityClasses\BoxLayout.as:88]
    at 
mx.containers::Box/measure()[C:\dev\flex_201_gmc\sdk\frameworks\mx\containers\Box.as:250]
    at 
mx.core::UIComponent/measureSizes()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\UIComponent.as:5448]
    at 
mx.core::UIComponent/validateSize()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\UIComponent.as:5394]
    at 
mx.core::Container/validateSize()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\Container.as:2688]
    at 
mx.managers::LayoutManager/validateSize()[C:\dev\flex_201_gmc\sdk\frameworks\mx\managers\LayoutManager.as:557]
    at 
mx.managers::LayoutManager/doPhasedInstantiation()[C:\dev\flex_201_gmc\sdk\frameworks\mx\managers\LayoutManager.as:646]
    at Function/http://adobe.com/AS3/2006/builtin::apply()
    at 
mx.core::UIComponent/callLaterDispatcher2()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\UIComponent.as:7909]
    at 
mx.core::UIComponent/callLaterDispatcher()[C:\dev\flex_201_gmc\sdk\frameworks\mx\core\UIComponent.as:7852]

Below is the code iam using when a tab is selected,

private function tabItemSelected(event:StringEvent):void{    
    var tabItem:String = event.str.toLowerCase();
    //tabs.cDisplay.removeAllChildren();
    if(tabs.cDisplay.numChildren > 0){
        tabs.cDisplay.removeChildAt(0);
    }
    switch(tabItem){
        case "usrSearch":
            var usrSearch:UserSearch = new UserSearch();
            tabs.cDisplay.addChild(usrSearch);
            break;
      case "ptCse":
            var ptCase:Case = new Case();
            tabs.cDisplay.addChild(ptCase);
            break;
}
}

Really appreciate any input.

Thank you.