This is an email registration dialog error – that function integrates with our Email Service Provider - MailChimp – and they seem to be having on an off issues with the integration of late.
If you have entered your Serial Number / Registration Code, then when you run SiteSpinner, go to Help > About. You should see your Serial Number there.
If that is the case then you can safely ignore that email registration error message. Simply select the checkbox to ignore.