Yup, my computer's connected to my 2Wire 3600hgv DSL router, which is in turn connected to the internet through AT&T's service. I heard that AT&T routers do block protocol 41, but since I'm running as DMZ 'plus' host, that shouldn't be an issue on AT&T's particular routers I also hear. Running as DMZ host on this router also gives my laptop my external public IP, as you can see from my original post.
Also, as I said before, turning off AVG does allow me to PING external IPv6 servers, like ipv6.google.com. The only thing is that I can't BROWSE to the actual site, and I also don't have an online web presence using IPv6, so no one can see my IPv6 address, which is what I need to pass the 'explorer' certification on HE.
As I said before, if no one knows how to fix the firewall issue, at this point I wouldn't mind temporarily turning off AVG to pass the certification, as long as I can fix the other problems and go on.
Went to test-ipv6.com and I failed a test.
Broken DNS AAAA Lookups
We detected that you are able to connect to IPv6 sites, by numerical address specifically. However, connections using DNS either failed, or preferred IPv4.
What does this mean for you?
You should still be able to reach most sites fine, so long as they offer their services on IPv4. This means few near-term problems.
Firefox users may have IPv6 lookups disabled.
Go to about:config in your browser.
Look for network.dns.disableIPv6
Make sure this is set to false.
Your OS may be configured to not do AAAA lookups; that is, to prefer IPv4 only.
Your DNS server may be filtering AAAA responses (or otherwise broken).
Some ISPs will intentionally filter AAAA records. For example, on World IPv6 Day, we expect many Japanese ISPs to filter AAAA records, to mitigate current IPv6 deployment issues unique to their environments.
You (or your techical support) can run dig @DNSSERVER aaaa aaaa.test-ipv6.com to confirm if the DNS server is working properly
Turns out the actual problem was that IPv6 WAS disabled in Firefox. XD
Next time I'll have to test with multiple browsers, probably Chrome or something though, as I uninstalled IE from my windows machine (lol).
Still though, if any of you have any solutions for the AVG firewall problem, I'll check back periodically.