Credit Card Error not shown to customer - Fast & Easy Checkout

I just realized, while manually running through checkout that the credit card error is not shown to the customer when they are redirected to the payment page.
I am using 1.3.8a with authorize.net AIM for cc processing. I am using numinix easy signup and login combined with fast easy checkout.
I can't find a setting in my admin panel. I don't know if I need to set a specific URL for this at authorize.net or if it may be the result of a combination with fast, easy checkout and auth AIM.
Any help would be appreciated!

Whoah. It looks like someone just moved this post and changed the title. I'm assuming this is some well-meaning moderator's way of better categorizing my post. However, it assumes the problem lies with FEC. Mod, if you know that's the issue, I'd appreciate your input.
I ran some more testing and a purposely incorrect credit card number kicks the page back with the proper error message. It seems that the problem occurs when it kicks back all the way from auth.net and may not be FECs problem at all.

Still haven't resolved this.