Scott, I no longer need the ability to clear the cart on the fly so you can forget about trying to find that information for me but I have another issue. I have no idea how you're storing the shopping cart items but the items are appearing across different users.
e.g. If I start out with a completely empty cart, login as a user and add an item, if I don't complete the payment process, logout, and login as a different user, the item the first user added is in the second user's cart (as well as the first). I imagine it would be in the cart no matter what user I login as.
I'm not sure if this is how your cart always behave, if it's a result from the custom programming we paid for, or a defect in the ?productid= querystring way to add a product.
Thanks