That's strange I can host on my wireless with norton
Edit: I got a couple of steps for you to try, fallow the pics
1)Open Norton
2) Click Settings in the Network Tab
3) Scroll to the Smart Firewall Settings and click Program Control
4) Find Warcraft III Change Drop down to Allow, Then click Modify in both screens that pop up.
5) Make sure all the settings match these ones. Leave the last 2 tabs alone, Exit everything restart Warcraft 3 and see if that works