Hostname www.dyndnscommunity.com is blocked in your defense plan.

Wow. I can't believe we missed this.

I added http://dyndns.stackexchange.com to the global override list on our backend for the content filtering. It will now always be available to everyone.

Sorry for the inconvenience!

You can report problems here at Barracuda since they supply the category information.

For the time being you can add either http://dyndns.stackexchange.com or just http://stackexchange.com to the "always allow" list of your defense plan.