This morning I was starting a LAN multi session, but as I started the game I got this error: "You have indicated that you use a LAN for networking. You also appear to be dialed into your ISP. Please disconnect from your service provider, or choose" and the message ends here.
Then I tried to host the game in the classic way... and I got the same error, despite having disconnected from LAN!!!
Now I can't play multi anymore...
Thanks for your help!