[flexcoders] scale9Grid: What am I missing?

[Amy]

I have my image set up just like in the docs
http://livedocs.adobe.com/flex/3/html/help.html?content=embed_4.html, 
but my image isn't actually scaling.  What am I missing?

This is my code:
[Embed(source='images/window.png', scaleGridTop='40', 
scaleGridBottom='185', scaleGridLeft='300', scaleGridRight='585')]
[Bindable]
private var windowImage:Class;

...

<mx:Image id="backgroundImage" source="{windowImage}" width="1000" />

The image is only 603 px wide, so it should stretch, but it's just 
sitting there like a lump.

Thanks;

Amy