One other tidbit, it is creating the user account and subscription even though it is throwing the error messages.
Registering the user is normal, because the user must be register to obtain a subscription.
The reason the subscription is becoming active is because you've configured it that way within your Offline gateway using the parameter "Payment selection leads to following order state:". It's set to give them a complete subscription and immediate access before you've confirmed their payment.
Have reviewed your install and I reviewed all of CBSubs language strings and this error doesn't exist anywhere in CBSubs. Doing some quick searching it seams the error is coming from AcyMailing. I was able to trace it to "CBSubs AcyMailing", which when disabled the issue is completely gone.
I then dug through AcyMailing and you had "Allow non-logged in users" set to "No". This meant AcyMailing wasn't allowing access to it self if the user wasn't logged in and in this case no one is logged in. This apparently blocks API usage too! Anyway, I set it to "Yes" and have confirmed it's working fine now. It maybe a good idea to suggest to AcyMailing that they do not block API with this parameter. Please also confirm that it's working fine now.
krileon
