How to set focus on fb:swf tags in Facebook app?

Question

My code is as follows:

<input id="input" type="text" onfocus="Focus('Input')" />
<input id="text" type="text" />

<fb:swf
    id="game"
    onfocus="Focus('Game')"
    swfsrc="http://ventoline.com/frozenbubble/preloaderbustamove.swf"
    width="640"
    height="480"
/>

<script type="text/javascript">
function Focus(msg){
    new Dialog().showMessage('Debug','Focus on: ' + msg);
}
</script>

When I run it through my Facebook app (canvas page), the 'Focus on: Game' message does not display, but the 'Focus on: Input' does.

You can try this for yourself if you like, you will see it as I do with a copy-paste of this source code.

Tried on Facebook developer forums and no joy. Hope the guys here can help, they have so many times before.

Cheers