This is the actual error message.
The host from which you are accessing the board is not recognized as a valid host. This is more than likely related to a firewall issue that is blocking the referer variable. Check your firewall settings and try again.

I have posted about 5 messages on my board, then had to go and change something in my profile and on the control panel, went back to the board to add another reply and got this message again.

I have had emails from most of my regular members and they all get this error, surely we should not have to disable firewall settings just to be able to post, and why was i able to post before on the board, and suddenly not now... (well not without clearing the cookie setting on the board?)