My iphone 4 doesn't recognize the built in speakers the thing is that it does sounds, but only the "system sounds" like when I lock it or receive an email. When I open any app that sound, even "music" app, the volume bar .. gone.. and when I use my headphones it's working. I have reset, restore, put it in dfu, nothing! It isn't with jailbreak and the weirdest thing that for a few seconds the volume bar reappear. please any advises?