Using 1.5.3 CiviCRM 4.6.26 on D7. I get the following error: "Invalid currency selection: USD for domain iatspayments.com" when I submit an event registration.
I believe I have the correct server url in NA for credit card payments: https://iatspayments.com/NetGate/ProcessLinkv2.asmx?WSDL
My event page is configured for USD($)