Hello,
I too have the same issue with the contact form’s spinning arrow remaining and never showing a success/failure message.
The contact form does successfully send the form email and also successfully subscribes to my MailChimp list.
I see no error messages anywhere and can see no logs in the plugin’s directory.
Versions are as follows:
WordPress: 3.8.3
Contact Form 7: 3.8
CF7 AutoResponder Addon: 1.7