is frozen.has connected symbol says eject before disconnecting

my sons i pod was working in the car last night pluged into the aux. when we got home he started charging it. when he went to unlug it it was frozen. i cant get the connected symbol to do anything. it says connected eject before disconnecting. i tried to plug plug it into the computer to try and restore it but the computer doesnt read the ipod. the cord is fine i have connected my ipod. i have tried holding down the center button nothing happens and i have also tried holding down the off button. when the ipod was charging it was in the locked position so it also show the lock in the upper left corner