Hi CM Support,
bit of a problem with the API the last few days. When we attempt to create new clients we are being presented with the Error 150 message on Client.Create.
The email address did not already exist in the account on Campaign Monitor but the error is thrown back to suggest it is.
This is a big concern for us as people registering on our site will abandon the site if they are getting this error when they should infact not (if not already in the account system).
Is there some issues with the API ?
I've just responded to your support request relating to this issue, and it appears that there is actually no problem with the API, but rather that there were actually calls being made to Client.Create from your account using duplicate email addresses.
Please see my response from support for details including logs of your API calls.