UBB.threads PHP Forum Software Community Forums UBB.threads 7 Version 7 Support Can't Post. Error regarding firewall

This is the 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.

We have no firewall blocking anything.

Using FireFox 19.0.2
UBB 7.5.4.1