See private message.
Based on the error message on the checkout page, the issue seems like it is on the ajax_wrapper.php page on line 22.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.