I recently worked through the difficulties to get IPv6 over IPv4 running as a dual stack on my network. I was extremely happy with it and it seemed to be working fine. The my wife asked me to install Norton Safety Minder on my desktop because it is used by our foster daughter during the day when I am at work.
Absolutely nowhere did I see anything to warn me that it would block IPv6 websites on any account, much less that it would block them on ALL of the computer's accounts including mine which is not monitored! I've been fighting to find out what the cause was for four days!
Tonight I loaded a VM with Win 7, made sure it worked with IPv6, then installed NSM. Bam, IPv6 doesn't work on the VM! So it is definitely NSM and it doesn't look like it was a corrupt install with it doing this on a clean, just stood up test machine!
It could be a default setting, which is one of the two reasons I'm posting this, to ask. Is this a setting in NSM that can be changed to at least get non-monitored accounts working?
Second, where was the warning about this? 
I couldn't even Google that this was the cause. I found one, just one post in this forum! It doesn't really say anything except someone else wants the functionality. No sticky, nothing!