[flexcoders] override updateDisplayList

[markgoldin_2000]

I am geting different results if I override updateDisplayList:
override protected function updateDisplayList(unscaledWidth:Number, 
unscaledHeight:Number):void 
{
super.updateDisplayList(unscaledWidth, unscaledHeight);
var rowBGIndex:int = listContent.getChildIndex
(listContent.getChildByName("rowBGs"));
var colBGIndex:int = listContent.getChildIndex
(listContent.getChildByName("colBGs"));
}
When I run it from production I am getting this:
TypeError: Error #2007: Parameter child must be non-null.
        at flash.display::DisplayObjectContainer/getChildIndex()
        at yardmodel.modulecode::RowColorGrid/updateDisplayList()
        at mx.controls.listClasses::ListBase/validateDisplayList()
        at mx.managers::LayoutManager/validateDisplayList()
        at mx.managers::LayoutManager/doPhasedInstantiation()
        at Function/http://adobe.com/AS3/2006/builtin::apply()
        at mx.core::UIComponent/callLaterDispatcher2()
        at mx.core::UIComponent/callLaterDispatcher()

But when I run from Flex Builder it works fine. I am not running 
againt same data, but is that a problem?

Please help.