I had an Iphone 3GS, which was jailbroken at version 4.2. I wanted to update it to iOS 5 or above and then jailbreak it again, because the current version is outdated. I tried to restore it on iTunes [I heard you weren't supposed to try and update it], but then it said restore failed, and gave me an error message (saying that it might be because I have unauthorised software or something like that). Now I can't do anything on the phone, because it's in "restore mode", but I can't restore it. What should I do?