xinxin on "Contact Form 7 not working on IXWeb sites"

I have a bunch of sites on IXWeb. I use Contact Form 7 on all of these sites and they have all stopped working.

I took one site and deactivated all of the plugins except Contact Form 7 - no go.

I checked the password retrieval system and password retrieval via email isn't working either.

So where to from here? What do I need to look at and what do I say to IXWeb support?

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

EDIT: I have just deactivated Contact Form 7 and tried the Jetpack contact form. That didn't work either so it must be a server problem. I have no idea where to start on this one.