403 error wpcf7_is_ajax_call

Hi,

I have a contact form on each page and for some reason, when I check the javascript console, I get a 403 error in the code looking like this:

http://www.domain.com/folder/?_wpcf7_is_ajax_call=1&_wpcf7=6869&_wpcf7_request_ver=1329185613485

What is causing this and how do I fix it?

Thanks.

https://wordpress.org/plugins/contact-form-7/