Hey, is your minecraft version on 1.8? You'll need to be on 1.8 to join MeepCraft. To do that, go to your Minecraft launcher > edit profile > 1.8 (this might be checked to 'latest version' already, so change it to the latest 1.8 version.)
Let me know if that fixes it; if not, it could be location or Internet based. I dont believe norton 360 would affect this.