Similar Situation
iphone 3gs 32gb 3.1.3 new bootrom
jailbroken and unlocked with spirit
I restored to factory settings through the iphone because I bought it on CL
I did the jailbreak and unlock so I know i have the shsh files on cydia
My problem: I have already altered the etc file in notepad, when I go to shift restore with 3gs 3.1.3 ipsw firmware it gives me the message cannot connect with itunes server. I got so annoyed that I couldnt restore to my previous software that I tried to just update to new factory 4.0 and now im getting the same message.
Im afraid I have bricked it because I can only put it in DFU mode or leave it stuck on the apple logo with the wheel.
Please if anyone has any ideas at all... Ive tried everything and searched endlessly
BTW im on windows xp home