this is going to be a long shot since i've never heard of anyone else that has done this, when I used to play wc3 I could never host until i did this (in windows xp)
right click your local area connection
click properties
You'll see Internet Protocol Version 4: click properties and manually enter in local ip so it doesn't change
back to network connections folder there should be an Internet connection icon, if there isn't google how to make it show with what operating system you have
right click that and hit properties
advanced tab
settings
hit add port and put in name and port (default for wc3 is 6112) make both TCP and UDP
in the name or ip of the computer hosting service: put in your local ip, although 127.0.0.1 might work
repeat with warcraft recommended ports if this doesn't work (but keep 6112 or whatever port you used as well)
also keep the port forward settings on the router
again i've never heard of anyone else doing this but it did work for me back when I still played and hosted games, this should work for windows xp and vista but I can't find how to make internet connection icon show in windows 7 so i cant confirm that for you