Minecraft 1.6.4 Multiplayer/LAN not working?

There was an update for minecraft and after me and my sister updated multiplayer weren't working. Me and my sister wanted to play minecraft and so I made a world and when she got on multiplayer she couldn't find my world. I turned on LAN and she still don't see it. When I got on multiplayer I see her world but couldn't get in. It said "Failed to connect server" in grey and in white it said "Operation failed" Help!