My iPhone is not playing music or app sounds. Yes, the volume is all the way up, nothing's muted, and the ringer is not muted. I installed the AudioAmp program from Installer.app, but I don't think that would do anything. What can I do? I know it's not a problem with the physical speaker, since there's audio when I put a call on speakerphone or when I receive a call from someone. Help!