SSL Error

We' re struggling to pinpoint the cause of an SSL error: Firefox says: Secure Connection Failed An error occurred during a connection to subscribe.wordpress.com. SSL received a record that exceeded the maximum permissible length. (Error code: ssl_error_rx_record_too_long) The error only occurs on our work network, so we' re wondering if there' s something we' ve set up incorrectly in our Fortgate (600C) box. Thanks in advance, Carl