I've just upgraded my phone to a nexus 4 from a Samsung ace, and so with it got the brand new jeally bean 4.2. In the sounds menu there's 3 separate sound settings; alarms, ringtone and then music/video/games. The music/video/games option is set to mute and I can't work out how to turn it back on. Touching the mute icon doesn't work, dragging the sound slider doesn't work. The rest of the sounds all work fine. Help?