It has been reported that quite a number of iPhone users have experienced problems after using the latest update. And some have been forced to restore to factory settings.
Some have found that their iPhones have completely bricked. One iPhone user updated their iPhone to 3.1 software then shortly afterwards tried to install an app, but the iPhone would not allow it.
When connecting the phone the next day the user was told that by iTunes that the iPhone would need to be restored, as it couldn’t be read. When eventually managing to restore the iPhone the user found the 11 of his apps were actually now missing, the user tried again which was an even bigger mistake as this totally killed the phone leaving it in recovery mode ands iTunes can’t restore it. Source – blogs.telegraph.co.uk