Menu screen comes up but cants play music?

I changed the earphone Jack and battery and it worked fine, but I noticed I left a small rubber piece out so I decided to put it back in. When I went to start the ipod, it went to the home screen and the display menu showed but did not react when clicking on it. The display goes to dim and I have to push the hold button to left and then to right and then it lights up again. I tried resetting with holding down center button and menu but it does it again. I tried putting old jack in and did the same thing. Have not tried putting old battery. Also I can't back up to Itunes because there isn't an option for it.