I have had a similar problem before. Try turning off your wii console, but take the disc out first, check the disc for any scratches. After that I waited about 10 minutes to let it cool down, then I tried it again and it worked. It could also be something to do with your MOHH2 profile.
I have the same problem m8... I get to the lobby, I choose the game, I get the loading screen then I get the famouse message: you have been disconnected from network. Even when I try to create a game I get same message. People tell you this and that but still remains problem unsolved. I have new wii and new mohh2