Myself and a few other people have always had trouble getting LAN games to show up for Warcraft 3, and before we've never been able to find out why.
About the only flaw we had was the host of the game must be running Vista. (It doesn't matter who started the hamachi network) If somebody can get this to work with the Warcraft 3 host being on XP, let me know in this thread.
First you must setup Hamachi:
Download Hamachi from: https://secure.logmein.com/products/hamachi/vpn.asp?lang=en
Install and setup Hamachi as you feel.
Join the network that you all will be using.
if experiencing problems you may need to open tcp ports 12975 and 32976 on your router, and\or set the Hamachi network device at top priority. Go to advance settings in your network device listing to do this.
WC3 Host:
Must be running Vista (again if somebody gets this to work right under XP let me know)
Host a LAN game as normal
if experiencing problems you may need to open port 6112 on your router.
Other players:
Download and install LANcraft from http://infoceptor.net/files/warcraft3.shtml
Type in the IP address of the person that is hosting (shown in hamachi).
Click start warcraft button
Go to the Local Area Network section and shortly you should see the game popup.
I got a few people in a game, and didn't have any problems, once we finally got it working.
Also if you are still having problems don't forget to check or temporarily disable your firewall.