Comment on WP Expander Plugin by SEO Dave.
The only difference I see between the demo site and your site is this class is missing:
My guess would be either you’ve not pasted all the code into a text widget (if you do copy and paste, I have no idea how it works) or the plugin assumes all themes use a li tag to surround widgets (not all themes do, Talian and Stallion included) and so you don’t get the ypn-widget class associated with the li tag (in Twentyten it’s associated with the surrounding li tag).
If you can get it working could be quite useful for Stallion since I’ve added widget areas in the header, below the header, above the footer and main content (you can have widget areas, like the sidebars anywhere on a page). Added them to allow for custom ads and more options for the current sidebar ads. You could for example add a custom ad where the main content ad is in Talian 5 and have it load after X seconds, might reduce ad blindness.
Don’t have time to play around with this concept before the Stallion release (few days with a bit of luck), but maybe for the next update.