Problem with upgrading Ip3g to 4.2.1

[Fokus]

Hello.

I have got Iphone 3g with 4.1 on BB 6.15.00,
And i can't update to 4.2.1 beacuse always i got 1015 error, Kickin out from recorvery didn't help, even i tried used to Custom firmware to update, still got 1015, when im trying do trick with Ireb (that one with green screen), i got error 16xx. There is anyway to upgrade to that firmware ?

[iYeow]

Make sure you have itunes 10
Run redsn0w 0.9.5b2 and browse to stock 4.1 ipsw
Check only the box DFU mode only.
When DFU is done, run Itunes and shift + restore to this file (it is in your PM box)

[Fokus]

Thanks for help , But when im trying to restore in Itunes, it says "Can't restore beacuse that file seems to be damaged"

[iYeow]

If you still want 4.2.1, then go and get a custom or make one yourself of custom 4.2.1 from pwnage tools 4.1.3. It is possible when i upload the file, it gets corrupted.
Or
You can restore to stock 4.1 , jailbreak it with the latest redsn0w and unlock with Ultrasn0w.