Have you totally rebooted it and updated the software ?
If not go to apple website and follow instructions to reboot ipod - this will wipe it clean and then install latest software for the ipod -(not itunes) this may cure the problem - I've only had to send mine back once - it was a very pleasant affair as it came back brand spanking new (if under warranty as Apple just replace them and dont bother fixing them.) I've had loads of problems - usually through dropping it - and a reboot etc usually cures it.