My code was working just fine with my developer account. I switched over to the production account in test mode, still worked. Now I'm testing on the production account in live mode, and every time I fill out the CIM popup (and I tried with both my cards, both of which worked before), I get the generic error "An error occurred during processing. Please try again." Since it's the hosted popup, I have no way of telling what the specific error code is, and I can't think of what would be preventing it from working. I did find a post here that said:
"If the transactions are working in test mode, this is most likely an error from the account setup. If you are receiving it for every transaction, than your Authorize.Net account probably isn't properly linked to your merchant account. This can usually be resolved by retrieving your processing parameters (commonly called var sheet ) from your merchant account provider and providing them to Authorize.Net support. For security reasons, that update has to be done over the phone."
I'm going to see if that works, let me know if there's anything else I should be trying as well.