Authorize.Net Settings - Fatal error: Cannot redeclare class AuthorizeNetARB

To further troubleshoot this, I have deactivated our store plugin, which is Shopp. Shopp currently has a payment gateway installed for access to Authorize.Net as well and this is causing a conflict between both add-ons.

I am not sure where to go from here.

UPDATE:
I looked into the files for the Authorize.Net addon. I found the AuthorizeNet.php file in:

plugins/gravityformsauthorizenet/api/AuthorizeNet.php

And commented out the line:

require dirname(__FILE__) . '/lib/AuthorizeNetARB.php';

Now, I have access to the settings without conflict. I could also disable the payment gateway for Authorize.Net in the Shopp plugin to get access to the settings without "Fatal Error."

Once I got everything set up I tried some test transactions with test and real credit cards. Receiving the errors for the credit card itself being incorrect.

Ideas?

I"m receiving this error too, is there any progress on this from support?

Since I am using Automated Recurring Billing through Gravity Forms and not Shopp, I renamed class in shopp plugin to avoid conflict.

plugins - AuthorizeNet - Authorize.net.php - Class AuthorizeNetARB