For the past week I can't adjust the volume on my ipod touch. the volume slider disappears. Sometimes it is there. I am not in landscape mode and don't use a docking station w/it. i tried restarting, resetting. I tried changing the music controls in Settings, but no luck. My ipod is 2 yrs old; i have 3.1.3 software. Is there any fix? i never had this problem before.