On Virtual Merchant all credit cards work on orders except for American Express which returns the following error...

Credit Card Processing Error: UNKNOWN ERROR
There has been an error processing your credit card!
An internal error occured during the communication with the Payment Gateway! Please try it again later. If this error occurs again, please choose a different payment option and inform customer support of this error at [email protected] ! Thank You!
UNRECOGNIZED_RESPONSE

Any help is greatly appreciated!

Thanks,
Matt
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Matt Frandsen
Code Red Labs