1) Reinstall the latest version of Ecart if you haven't in the past month
2) Delete the file: WA_eCart/WA_DMCFG.xml
3) on a new blank page add a shopping cart to the page with the eCart Display Manager (you can delete the page after)
4) Run the checkout wizard again
If you still have issues I'll have to set up a screen sharing session to debug it. Please post a US phone number or Skype contact information in the private area and I'll contact you to schedule a good time.