I had understood that all I had to do to use Authorize.net with CubeCart was to edit the gateway settings with the Authorize Login ID and the Authorize txnkey and enable the status. However, when the checkout gets to "building order . . ", an error screen is returned of "(103) This transaction can not be accepted."

Authorize.net says I must have a SIM (Simple Intetgration Method), and sent me a 62 page PDF file about it.

Any advice would be greatly appreciated.