If you experience this issue on a Mac, disconnect third-party devices, hubs, spare cables, displays, reset the SMC, and then try to restore.If you are using a Windows computer, remove all USB devices and spare cables other than your keyboard, mouse, and the device, restart the computer, and try to restore.
Permission error either on your computer or the device. This occurs when the media library on the device is corrupt and cannot be modified or updated.
The App you've tried to download in i Tunes couldn't be saved. Use Tiny Umbrella or redsn0w to kick it out of Recovery Mode.
In case this is not working use Pwnage Tool to create a custom firmware WITHOUT the i Pad baseband, put your device in pwned DFU Mode and restore via i Tunes.
Bad response from gs.OR need i REB for preparing the device for restoring to custom IPSW When Spirit2Pwn flashes parts of the boot chain on i OS 4, the device may crash into DFU Mode. Restart computer; change USB port; reinstall system. Restart computer; change USB port; reinstall system.
Some have seen success afterwards by doing the downgrade from DFU mode instead of the normal Recovery mode. This is caused by a failure to match the Baseband Nonce currently in memory to the nonce returned in the Baseband Firmware SHSH blob.