Hi
I have previously opened a case where we had problems in activating "email permissions" by using a Forms module http://manual.dynamicweb-cms.com/Default.aspx?ID=6661 and the @Form.Checkbox.SubscribeToNewsletter tag (where the user gets created under the right category(folder) but email permission does not get activated).
According to your support team, the error happens because the Forms module supports Newsletter v3 but does not support the E-mail marketing module (as in it does not "allow emails" on the created user).
It would be great if you could add support for E-mail marketing on the Forms module, since the only thing that is lacking at the moment is the "email permission" and I presume it would not be a very complicated fix for you.
Best regards
Bogdan / Smartpage