Bert,
Have you ever considered using OpenDNS. It installs nothing on any computer all you need to do is setup your router with OpenDNS's ip address for DNS and then put your static (or setup a Dynamic Updater) for your IP Addresss. When a computer coming from your IP makes a DNS query for blockedsite.com it checks to see if its on the blocked site list. If it is, it redirects you to a blocked page. If not it lets you thru. Its pretty robust and I dont think anyone will catch on to the fact that is all done through DNS. Some routers (DD-WRT or Tomato based firmware) can be set to not allow or "catch" all port 53 requests(DNS) and send them to your dns servers of choice thus not allowing a end user the ability to point to another dns server. You can also do this is better routers Cisco Systems Integrated Service Routers, etc.
This solution also can block categories at a time.
Perhaps its not worth your time to reconfigure your website blocking software if you already paid for one. I just like how opendns is all managed from one website and applies to EVERYTHING connected to the network.
PremiumDNS from OpenDNS is also free, and what I love about it is there is nothing "extra" installed on the computer to take up resources and space.
