I have always had this problem on my pc, but today it happened again. I tried to jailbreak my iPod using blackrain, and when I opened up the application, it gave me some error and wasn't able to install cydia. So I figured it was because I didn't have 3.0 jailbroken when I updated. I try to reinstall the 3.0 firmware, downgrading, and it went through the extracting software part, and then gave me this. The iPod "Mike's iPod" could not be restored: an unkown error occured(20). Before the error was always 1604. It isn't bricked, I can still restore to 3.1.2. But nothing else. Any help is appreciated because I would really like to jailbreak.