DNS Norton

Greetings, excuse my English is not my native language. I have long been using Norton DNS (199.85.126.20 - 199.85.127.20) Community PC in my house, to prevent full of crap when my horny nephews used. As you know, these DNS block malicious sites and pornography.

Until recently I worked smoothly, the point is that yesterday I came give maintenance to the PC, go malwarebytes, superantispyware, antivirus and ccleaner, I came across several cookies adult sites. Thinking they had altered DNS check, but they were mentioned, I tried to access a page for adults in the browser and I allowed it smoothly, above, I skipped message norton safe preventing it.

To verify that the error was not PC, change the DNS of my personal PC, I use of google, by Norton, but also allowed me to access the pages that should be blocked.

No it can be happening, if not a thing of the DNS Norton, or my ISP, which made updates on your system and has been a mess for almost a month, falls, blocking pages ago, keep going.

My scans with Eset Smart Security 9 and Norton, leave pay, malwarebytes and superantispyware come clean on both PCs.

That may be preventing the Norton DNS does not block sites?

Thanks in advance.