[flexcoders] Tabbing not working on component with text inputs

[dorkie dork from dorktown]

I have a simple MXML component with a contact form in it. This contact
form has 4 TextInputs, a TextArea and a Submit button. When I place
the cursor in the TextInput and hit tab it doesn't move to the next
tab input. If I press tab repeatedly it doesn't cycle back around like
I'd expect it to. Is there something I am doing wrong? This is a Flex
4 project. Here is the component code:

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:fx="http://ns.adobe.com/mxml/2009";
                 xmlns:s="library://ns.adobe.com/flex/spark"
                 xmlns:mx="library://ns.adobe.com/flex/halo" width="100%">

        <s:RichText x="0" y="10" text="Leave a Reply" fontWeight="bold" 
fontSize="16"/>
        <s:TextArea y="124" height="155" id="commentText" width="100%" 
tabIndex="4"/>
        <s:HGroup y="35" verticalAlign="middle">
                <mx:TextInput width="170" id="authorText" tabIndex="1"/>
                <s:RichText text="Name (required)"/>
        </s:HGroup>
        <s:HGroup x="0" y="65" verticalAlign="middle">
                <mx:TextInput width="170" id="emailText" tabIndex="2"/>
                <s:RichText text="Mail (will not be published)"/>
        </s:HGroup>
        <s:HGroup x="0" y="95" verticalAlign="middle">
                <mx:TextInput width="170" id="websiteText" tabIndex="3"/>
                <s:RichText text="Website"/>
        </s:HGroup>
        <s:Button y="287" label="Submit" right="10" click="form1.send()"/>

</mx:Canvas>