The iPhone could not be restored. An unknown error occured (1600) ???

[camnu]

Hi,

Year ago, I unlocked my 3G iPhone to version 4.x.x. It worked fine. Recently, I updated to version 4.2.1. I can jailbreak it, then I tried to unlock it by using ultrasn0w. The installation of Ultrasn0w went well (I've unlocked successfully 2 other iPhone). However, the iPhone keeps saying "No Service". I've tried to redo and re-installed 3 times, but all in vain.

Next, I tried to restore the iPhone as initially (I'd like to start from scratch). The process went on for a few minutes. It ran good, till the end where an error message pops up: "The iPhone could not be restored. An unknown error occured (1600)".

Now I could do nothing. I can't jailbreak it with Sn0wbreeze, neither with RedSn0w. I've always ended up with that message.

Could you please tell me what I should do now. I'm quite desperate.
Your help is greatly appreciated.

[iYeow]

What version of itunes do you have ?

[i.Annie]

Restore to stock (not custom) 4.2.1 firmware. Then use redsn0w to jailbreak it. Error 1600 occurs when you try to restore to a custom firmware without setting your device into pwned dfu mode properly.

[camnu]

Restore to stock (not custom) 4.2.1 firmware. Then use redsn0w to jailbreak it. Error 1600 occurs when you try to restore to a custom firmware without setting your device into pwned dfu mode properly.

I use the latest version of iTunes.
I did try many times to restore to the factory settings, but all in vain. The same error message pops up at the end.
Thank you for your help.