Network error with LAN games

[SBFC]

Hello all, I was at a LAN party tonight and while my friends were playing Enemy Territory I couldn't see their game via the game browser and noticed this in the console:

Scanning for servers on the local network...
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27960
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27961
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27962
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27963
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27960
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27961
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27962
NET_SendPacket ERROR: Network is unreachable to 00000000.000000000000:27963


Does anyone know what causes that?

I also couldn't see the HL2 server my friend started, yet when I started one he could see mine and connect to it.

Now that I'm home I started up my ET server to see if the problem remained, but everything works fine.

I don't understand what would have caused that.

We were using a few switches to connect all our computers. I can't think of any other information to provide that would be useful. If there is anything that would be of help, please, let me know.

Thanks.