I've had no problems turning off A/V, firewalls, etc...but I wouldn't recommend leaving it that way.
So you say you ONLY use Norton 360? Window's firewall is off, no router firewall's or anything like that?
You can try this see if it helps you...
http://www.youtube.com/watch?v=7K8XXqyRMbs&feature=relatedhttp://service1.symantec.com/SUPPORT/norton360.nsf/0/c7cddb1ba72b95036525736800684073?OpenDocument&seg=hm&lg=en&ct=usAgain though, easiest thing would be to turn off Norton 360 and see if you can host. Just do it as a test, no need to have it on long, you can even make the server private so only you can join. If it works, then I'd try to modify Norton, if not then there has to be something else. My issues had to do with my router.
I figured though you wouldn't be able to just delete it. Maybe though you can approach your parents letting them know that they are wasting their money

...Norton is a huge resource hog, and really isn't any more efficient than the freeware. I think they make it harder to use as they limit the options you have when it comes to adjusting it, and of course you have to pay them monthly which is BS. For what they give you it's a complete rip-off, IMHO. Anyhow, if not leave it as it is

...I know what it's like trying to explain these type of things to people who are just too cautious.