Security Meltdown

I had planned on writing a post yesterday addressing Internet safety for children. Ironically, we experienced somewhat of a security meltdown on our computer before I even got a chance.
It started early yesterday morning. My husband and I were noticing annoying pop ups on most sites. No matter what we did to try to block them they kept coming. Although we were able to get an Internet connection we were denied access to any HTTPS sites which includes our email and my classroom portal.
While we were running all kinds of security checks and scans I questioned my sons about the NeoPets site they had been on. They are very conscientious about asking permission before they click into anything new. I asked many questions regarding anything unusual they may have experienced on NeoPets. They insisted everything had been normal. Finally, I asked them specifically about pictures of naked people. Oh, yes, they said there had been plenty of those! What an eye opening conversation. It worries me that they never brought these to my attention at the time and didn't think even think them important enough to mention when I was asking about NeoPets. Up until now I had few concerns about allowing my children on the Internet. They are generally very responsible and careful. However, I realize they are also children. They are naive and trusting. Just recently I had added some parental controls to our computer but to my chagrin they had been disabled. Apparently there is no substitute for old fashioned adult supervision. I will therefore be much more vigilant in my monitoring of their computer use. There is simply no room for complacency. Although we are able to get into secure sites now we have been unsuccessful at getting rid of the pop ups. We uninstalled and reinstalled Norton Security to no avail. If anyone has any suggestions I'm all ears.