We were experiencing a similar problem. It is due to Symantec’s partial support of IPv6; you cannot specify any type of range for IPv6 so you cannot distinguish between local and remote network traffic I had to change some of the rules to allow All Hosts for things like ICMP and LLMR. I was ok in doing this as I have a fierwall device blocking all that from the outside. It was just my internal computers causing the popups.
I noticed issues with connecting to some Google Services if I completely disabled IPv6. You might try the option that tells windows computers to prefer the IPv4 address rather than disabling it all together. The instructions are in the same KB article that .Brian recommended.
Hope this helps