iphone 4 6.1 update error (-1)

[cornel.virlan]

HI, I have an iphone 4.Was working fine on 5.1.1 + jailbreak.I want to sell it so I tried to make a clean restore on itunes. The process was going well but almost at the end it gave the (-1)error. Now the iphone is stuck in recovery mode and I don't know what to do with it. I've tried the following:
-retried official itunes restore on windows, mac
-changed the motherboard on another iphone that was 100% working, still error -1
-there are 5.1.1 SHSH saved so I stitched the blobs to the ipsw and tried itunes in pwned DFU, still with other errors.
-I tried restoring with redsnow to the 5.1.1 and still nothing. I can't get out from recovery mode as redsnow does not support 6.1 and tinyumbrella has no effect. Maybe someone can give me some new ideas or know why this happened. THanks