stefswaters on "[Plugin: Contact Form 7] Contact form 7 error"

I have a strange problem with the contact form 7.

The contact box works fine on the "home" page, but on all the other pages where i have insert the contact box it doesn't work.

Check this out on http://www.ridderhertog.nl

Can anyone see what the problem is?

Thanks in advance!

http://wordpress.org/extend/plugins/contact-form-7/