Try deleting the file: WA_DMCFG.xml
Then create a new blank page and create a cart display with the Display Manager so that the file is recreated. You can delete the page after.
Then run the checkout wizard again and see if that fixes it.
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.