This looks to be a message about your account settings with Authorize.net, here is a link that i found to a forum post about the same issue:
When you are running your tests are you using the same credit card and billing information each time? Do you get the error everytime when you use this credit card and details? What about the items you are testing with, are they the same everytime? I wondering if you have a value that you are using somewhere along the way that is causing this error. It seems that it is your merchant account that has the problem, the error is not mentioning anything about the values you are passing or credentials.