Items Being Added That Cust. Did Not Order

[Guest]

We are having a problem with our catalog and really don't even know where to begin to look for an answer.

 

Items are being added to orders that our customers have not ordered. I have went in to the site as a customer and duplicated the error and this is how it goes--I place the order, enter my info, enter payment and shipping info, confirm the order---and at this point the order is correct----submit the order, get the confirmation that is also correct at this point, and get a confirmation email as a customer that is correct. But going in through the admin section under our pending orders, there are two orders posted at the exact same time for random different amounts with different sales tax and shipping. There will be the entry for the correct, original order, and an entry for a bogus and completely random order listed in the pending orders. When I pull up the invoice of either order, the orders come up in the invoice as combined. The confirmation emails that we get as administrators are showing the correct order---without the additional items. We have to remove the additional items to process the order without charging the customer for items they didn't order.

 

Where do we begin??

Thanks