this exact thing happened to me last night, i wanted to use my ipod to relax before i went to sleep because i don't like going to sleep stressed out over school and relatioships and other stuff.. so I grab my ipod and its in disk mode.. i tried plugging it into my computer and it did not work.. so i tried plugging it into my laptop and still nothing.. so I held down play and the center button.. still nothing... i did get a solution though.. after 10 minutes of doing everything i know with the ipod..

solution: hold the center button and the menu button.. it goes back into normal mode.