i had the same problem, just listen, let the ipod die, plug it into your computer that has what you used to jailbreak it with, once plugged in (if on redsnow, hit extras then just boot tethered) just go into DFU mode( hold sleep for three seconds, then without releasing hold the home button for ten seconds, then release the sleep button and keep holding the home button for 15 seconds) then should reboot your device