My iTouch 4G will not change the Volume Level!?

I've recently got an iTouch 4G 8GB for Christmas, and it worked out excellent, the way it should. But it's been a few days after Christmas, and now my iTouch lags for some reason. When I change the volume level with the two ons on the left side, it will not display the volume picture in the middle of the screen. So I go to Home, click General and select Sounds. I change the Volume Level through the volume changer. So then I go to an app with music, and it doesn't display the music. So when I go back to General and change the volume settings, I can hear the sound effect of my Ringer.