The reason for this is because the settings in your Authorize.net virtual terminal are out of date for the version we are using.
Login to your Authorize.net account >> Go to Settings, then to Transaction Version. This should be on version 3.1. If you are given the chance to upgrade to 3.1, make sure you do. If you are just on version 3, it will cause problems with our software.
Next, go to Receipt Page, then to Receipt Method. The Receipt Link URL should be blank, and the Receipt Method should be GET. Then go back to your settings, and go to Relay Response. This should be blank as well. Now go to Direct Response, and make sure that the Delimited Response is set to YES. The Default Field Separator should be ,(comma).
This also applies to strange things happening with Authorize.net (such as some orders not coming through, payment info not always returned, etc. etc.)
