My wife has a new Galaxy Mini running android 2.3 gingerbread. She came to me all upset as the music file she was playing was barely audible. She had previously listened to it at normal sound levels earlier. Pressing the volume control button on the left hand side of the phone up did not make it any louder. I found that rebooting the phone solved the problem. Upon reboot the sound returned to the normal levels. I’m not quite sure what caused the problem. Possibly a misbehaving application. Anyway she is now happy. So the motto about rebooting computers solves 90% of computer problems also holds out to mobile phones!