I did this:
- followed your link above
- clicked through to Products Page
- added your item to cart
- could not find Checkout link; clicked a few menu links, clicked link to Product Page again, Checkout link appeared
- filled in form, including CC fields
I see you've currently disabled wp-e-commerce. Is it that you can't find the Checkout page, or that you get a Checkout page with no CC fields?
Off topic, but: why are you loading a really old version of jQuery, and why are you putting script into the page before even the DOCTYPE declaration? Use wp_enqueue_script to load scripts and define dependencies like jQuery, and use the one bundled with WordPress.