What's wrong with my iPod?

I got this new speaker(Altec Lansing IMT620) I tried plugging my iPod touch 4 into the iPod slot, but its not working. I tried my iPod nano in the same slot and it played. My iPod touch is still charging and playing. The Aux is the only part working in the stereo so what's wrong. When I plugged it in 2 nights ago it worked fine, but since yesterday it hasn't played through the iPox slot. HELP!