My b2evolution Version: Not Entered

b2 v. 4.0.5
url. [url=http://www.andyp.me/blog1.php]andyp.me[/url]

I seem to have an error preventing feedback on my blog, (link above). This was reported to me by friends and I just can't fathom out why.

Trying to post feedback, as non member - not logged in, after entering name, e-mail, message etc. when the send comment button is hit I and they get the following message;

Incorrect crumb received! [comment]
Your request was stopped for security reasons.
Have you waited more than 2 hours before submitting your request?
Please go back to the previous page and refresh it before submitting the form again.

Alternatively, you can try to resubmit your request with a refreshed crumb:

I've been through every possible setting I can think of and can't find out why this is happening. In my blog2, a hidden but sort of mirror, this doesn't happen.

Ideas and especially solutions would be appreciated as this is driving me crazy. What use is the blog if people can't comment :(