HELP! There Are No Items In Your Shopping Cart

I have created a product:
http://treethugger.com/store/products/chalk-dust-torture-charlie-brown/

You can add it to your cart.
The sidebar widget updates correctly.

Click on checkout takes you to the shopping cart page.
The page displays one lone line of text "There are no items in your cart."

Ive searched the forum and read about 20 posts. Cant find anything. Please help!