My iPad suddenly have no sound! The volume key is not working as well! But under the following condition, it works: 1. When I use headphone, everything is normal. The volume key is working too. That means the sound chips and the volume key is working. 2. When I play Magic Piano, everything is normal too. Music is coming out from the internal speakers. The volume key is working too. That means hardware of my iPad is normal. But, all others Apps, even Video or iPod is not working, no sound from the internal speakers and the volume key is not working too! Tried to reset all and also restore the firmware. It won't help! Still the same! Any suggestion?