U2 20Gb iPod won't unlock

If the restore was successful, there's no reason why the padlock should still be there. A successful restore will remove ALL content from the iPod, including all settings (which includes the screen lock.) I would try forcing the iPod into disk mode (reset the iPod by holding the menu and center buttons together for 6-10 seconds, then when the apple logo appears, hold the center and play/pause buttons together until "disk mode, ok to disconnect" appears), and attempting the restore again.

I had that SAME issue with the same ipod. That iPod edition is honestly nothing but problems, I've had to replace it at least 7 times. But I discovered if u like squeeze the sides of it in a certain way, it'll unlock for a second long enough for u to slightly change the song or scroll a little bit, but im not sure if theres much u can do.