Hellow, my flex is going strange again..

People usually like using 'tab' key when inputin some data, or whatever that make it faster and easy,,
but i got some error trace, i dont know why..

Here is the trace
ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
at flash.display::DisplayObjectContainer/getChildIndex()
at mx.core::Container/getChildIndex()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Container.as:2407]
at mx.containers::Panel/getChildIndex()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\containers\Panel.as:1032]
at fl.managers::FocusManager/getChildIndex()
at fl.managers::FocusManager/sortByDepth()
at Array$/_sort()
at Array/http://adobe.com/AS3/2006/builtin::sort()
at fl.managers::FocusManager/sortFocusableObjects()
at fl.managers::FocusManager/keyDownHandler()Thank you very much
