If your on a PC, no need to restore!
Plug in your iPod
Go to "My Computer"
Open your iPod's drive (usually the F Drive)
Make sure you can see all hidden folders (If you aren't sure go to Tools, Folder Options, View Tab, and check Show)
Open the folder "iPod_Control"
Open the folder called "Device"
Rename the file "_locked" to "_unlocked"