Generally when your iPod becomes "frozen," (the iPod either stops responding or will not wake from sleep), Apple recommends a few simple procedures including leaving the unit unplugged for 24 hours. For some users, however, none of the suggested solutions restore normal functionality, and units are sent in for repair.
MacFixIt reader Robert Snell, however, found that temporarily opening the case and disconnecting the battery for a short period of time worked:
"Before sending it back for service, I decided to try resetting the unit by opening the case and disconnecting the battery for a short period of time. After reconnecting the battery, the Apple logo appeared and operation was returned to normal. Measuring the battery voltage revealed it to be fully charged.
"Also, be very careful NOT to accidently short out the battery when disconnecting it. Since the "off" battery discharge time is about one month, I would have waited a long time for the power down reset to occur."
"This occurred after returning from a trip where my iPod had been through several X-Ray inspection machines and it was fully charged before I left."
For more information about the iPod's battery, visit the recently published iPod Battery FAQ.