I have a weird issue (weird because it is specific to one component) with applicationComplete in a fairly simple application. All the UI components are declared in MXML. I can access them all in applicationComplete, but not a spark.components.TextArea component, named taStatus here; it is null in the handler.

MXML looks sort of like this (there are lots of other components, but nothing special)

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="710" minHeight="640" applicationComplete="onApplicationComplete(event)" width="710" height="640">
    <mx:TabNavigator left="15" right="15" top="15" bottom="340" paddingTop="0">
        <s:NavigatorContent label="General" width="100%" height="100%">
            <s:Label x="93" y="71" text="Label" id="lblTest"/>
        </s:NavigatorContent>
        <s:NavigatorContent label="Status" width="100%" height="100%">
            <s:TextArea id="taStatus" width="100%" height="100%" text="Startup." editable="false"/>
        </s:NavigatorContent>
    </mx:TabNavigator>
    <fx:Script source="main.as" />
</s:Application>

Here is the handler in main.as

protected function onApplicationComplete(event: FlexEvent) : void
{
    lblTest.text = 'abc789';    // OK
    taStatus.text = 'abc789';   // Fail 
}

TypeError: Error #1009: Cannot access a property or method of a null object reference. So taStatus is null... What is so special about this TextArea?