1) Check your internet connection, make sure the wiiconnect24 is on. Homebrew Channel will work if it is already installed prior to the update to Wii 4.0, and HBC will work even if there is no internet connection... however it will not update or launch certain apps without a stable internet connection.
2) Some applications may be disabled on 4.0, but I don't know the specifics.
It sounds like the problem is a network issue though. Try to resetup the network.