Orders coming through without any products

I have quite a few customizations, but the only one, I know of, that would effect the checkout process is exclusive to admin orders.

The payment methods I have enabled are Credit (using Authorize.net), Check and "Free Order". The last explains why these orders are being set to "Completed". The "Free Order" payment method is automatically triggered when an order total is 0, and all the orders in question happen to show this as the active payment method.

It would make sense to me, then, that the error is occurring before the hook_uc_payment_method_checkout_alter() method is called. Is it possible the customer could be making it to the checkout page without products in their cart?

Here's an example of one of the products customer's are trying to purchase when they receive this error: http://www.thebuffmom.com/boot-camp-class/cambridge-evening-1. (It's a website offering boot camp classes for moms)

Sorry for the delay...

I am using http://drupal.org/project/uc_discounts_alt for discounts. There are about 4 discounts on the site, created by the client. I've tested each, and am able to get to the review order page with my cart intact. I'm also not sure if this is the issue, since none of the orders in question show that a discount has been applied to the order. Also, if it was a problem with discounts, I would expect to see an issue with the subtotal, not an absence of products altogether.

At first I thought the fact that products have no price until options are selected might be the cause. But as much as I've tried, I can't get to the cart without selecting some option first. Plus, if that was the issue, I would expect to see an order with products that have a price of $0.00. But again, no products are in the orders at all.

It's strange, because it should be impossible for a customer to checkout without any products in their cart. But that seems to be what's happening. And I know it's not some rule that's completing the order before the customer has checked out, because the client found out about the issue from customers who checked out, and received an invoice with a $0.00 order total.

For a while there were a cluster of orders like this happening, but I haven't seen one in over a month. Perhaps it was related to some product, or discount setting the user created.

I decided to add a custom validate handler to uc_cart_checkout_review_form(), so I can detect if at this point the order doesn't have any products. I'll update this issue if I find out anymore information.

Thanks,