Jedateach - I understand that the plugin is old but in the meantime, I'd like to be able to troubleshoot it a bit before just upgrading and not knowing if I've solved my problem or not. Any ideas as to what is causing this? I really do appreciate the help as I'm a bit stumped.
Logically, the module would kick the user back to the payment process if the full value wasn't processed, thus leaving an outstanding value. What I can't seem to understand, though, is why AuthorizeNet would even allow a credit card to only process a portion of the payment - seems like it should be all or nothing. This makes me believe that the full value isn't being passed into AuthorizeNet in the first place.