I've just had an email with the same thing...
I'm having big problems posting mate. FF and IE7 both give a UBB error.
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???
Surely he will be using a firewall. But why is this error happening only sometimes? This guy is a regular user.
