hi,
i accedentaly upgraded a 1.0.2 version to 1.1.3 the phone had no service complaint and i was trying to fix it.
now when i try to downgrade to any lower version eg 1.1.2,1.1.1 or 1.0.2 i get error(1).
any solution to fix this phone
regards
gopal

SEARCH THE FORUMS!!!!!!!!!

Tutorial Downgrade 1.1.3 -> 1.1.1 WINDOWS] How it works
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Found this tutorial at iphone-forums.de (german)
I'll try to translate it:

1. Connect iPhone with PC
2. Download iPhuc http://**********.com/files/84214672/iPhuc.zip
3. Unpack & start iPhuc.exe
4. Type in "enterrecovery" and wait until iPhone enters Recoverymode (Notice be sure you are on iTunes 7.5 and its running while doing this tut!)
5. iPhuc window should say: <iPHUC Restore> #:
(If not, restart iphuc.exe)
6. Type in "filecopytophone WTF.s5l8900xall.RELEASE.dfu"
7. Type "cmd go"
8. Wait until iPhone Screen turns white and iTunes recognizes a device connected to it
9. Hold down shift + restore -> choose FW 1.1.2 -> let it finish -> do the same and choose 1.1.1 fw
10. Use iBrickr to kick the phone out of the DFU and go on as usual

All fame goes to puma_hh & kIREmK @ iphone-forums.de

if you wanna use it as phone again you will need to downgrade the baseband as well. This one I leave to you and your search skills

Hi, I got the same error (1), and I searched and read almost every tutorial for downgrading 1.1.3 to 1.1.1 and couldn't find a solution.
The iPhone does not want to do a restore to any firmware with iTunes.
And finally while attempting to kisk it back with iBrickr i got a screen full of letters and the phone just keeps restarting all over again. Nothing helps, does anyone know how to fix it?
I ttryed iBrickr, iDemocracy and a different version of iTunes (7.4) on another computer, and still nothing! It just keeps restarting endlessly.