I have experienced the same issue when I set a parental rule, but my speed goes down to a crawl. FIOS 15/5 service. I manually assign IP's to the kids computers, then use the IP address's to build the rules around. I have tried just using set time blocks (without web address blocks), and just certain web address blocks (with no time restrictions) and either way all the PC's at home come to a crawl when accessing the internet (even those with no rules on thier IP address). I gave up a after a few weeks when I finally realized the connection between having rules and the slow speed and deleted the rules all together to keep the internet speed up.
Has anyone come up with a solution. I have the actiontec router that is black and silver (not the first generation actiontec that was a huge black brick).