Last time it happens to me I had to send back too apple with the warranty ... Call them to make sure it's not something you can do on you're own espacially if Itunes don't see it!
You probaly need to contact the apple store. I thought you was having the same problem I had when my computer didn't recognize my touch and it didn't charge. But what I can suggest leaving it unplugged for q few hours and try again. Still no success? Then try plugging it into a computer/laptop then hold home button for a few seconds then continue to hold home+sleep button for about 20+ seconds and see what happens. That doesn't work then hold home and repeatly press the sleep button. I tried this and my iPod work again. Sorry if it doesn't works for you.