I think it may be my new computer, but I don't know. I remember thinking about this a while ago when I hosted a LAN server for me and my cousin, and he couldn't connect. More recently, my brother hosted a LAN server, and while my sister could connect, I had to go through the direct connect to finally play. I can play online servers without any problems, it's just LAN that won't work without direct connect.
What's really weird is that I have no problem joining and hosting Terraria LAN servers. It's just Minecraft that has so far given me this issue. I've tried turning my firewalls off, but that didn't seem to help as I still could not connect.
By the way, this is all in Minecraft 1.7.2. Don't know if that means anything, but that's that.
Any suggestions?