My iPod has frozen - help!?

My iPod has frozen. The clock is working fine, but that's all that's working! It's stuck on the clock screen and won't budge. I've tried charging it, holding down the play and middle ons together, likewise with the menu and middle on. It switches off when I hold down the play on, but when it comes back on, it's still frozen on the clock screen. Any ideas what I can do? I can't live without my iPod! Help!