Sorry, I wasn't sure if I should post this here, or on the page for the Authorize.net Advanced (CIM). It is also located here: http://www.ubercart.org/contrib/2537#comment-24595
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This is an issue with v0.83 of the Authorize.net Advanced (CIM). See a live example of the problem by visiting this site: http://www.chrismartenson.com/join_now
Add a subscription in the shopping cart and then click "Checkout". Complete the credit card and billing address information, selecting "Canada" as the country and "British Columbia" as the zone. After clicking "Review order", the following error message is displayed:
An illegal choice has been detected. Please contact the site administrator.At this point the zone select dropdown has been populated with US states. If I select a US state and then click "review", I receive the error again ... but this time the zone reverts back to Canadian provinces. If I now select a province and click "review" again, it successfully takes me to the Review Order page.
Re: Illegal choice error when selecting non-US country
We got around this by not using the CIM payment form, and instead using the standard Ubercart Authnet payment form. It is detailed in the CIM instructions how you can use the AIM form as part of checkout instead. The standard form works correctly for all countries.