I have been playing LEGO Harry Potter: Years 1-4 on the Wii but recently the game has been freezing. I cannot enter Diagon Alley, nor can I continue the game. I am on Year 4, Level 2, but as soon as I try to advance to the next room to follow the ghost, the game freezes: the tv buzzes, screen stays black, and to fix it, I have to unplug the Wii. I can take the game out, but I can't turn off the Wii without unplugging it. Any help?