We both disabled our Firewall's, still no world is showing up. I've been researching into this problem and it seems that Hamachi is a problem for most people. We both checked, Hamachi is not on either of our computers, so that can't be the problem.
It's a common issue - even when both/all parties have the windows firewall completely disabled it just doesn't work for a lot of us, LAN or Hamachi.
For a few people, using the IP in Add Server or Direct Connect can work, so while it's not a perfect solution to what are some pretty obvious LAN server hosting/detection issues, it might help until they are presumably solved.
ok, i also had this problem for a LONG time. But the answer is simple... your computer is not letting other computers connect to your computer through the internet connection, this is how you fix it:
1. click start, then control panel
2. click on Network and Internet
3. click on Network and Sharing Center
4. find your connection on the right hand side
5. click on this connection in blue next to 'connection:'
6. click on properties, the one with the shield thing
7. up the top, click on sharing
8. tick that box where it says to Allow other network users to connect.....
9. under 'Home networking connection: select 'Local Area Connection'
10. click 'ok'!