DW CS4, Ecart5, PHP, PayPal Payments Pro Sandbox.
Everything seemed to be working, except when I click on the final checkout (from the Confirmation Page - pp-confirm.php) I get "Duplicate Entry "0" for Key 1".
NOTE: This is after going to paypal, and coming back to the confirmation page. Then I click Checkout and get this message.
What does that mean and how do I fix it?