Hallo,
yesterday, i got my new iphone 4g, then i jailbreaked it and installed a lots of apps. After that i realized that an app that i have installed doesn't run and so it crash each time i tried to start it. As a matter of fact i deleted this app and installed the same one in another version with the result that my iphone 4 needed to restart. In the time while my iphone restart, at the moment the boot logo appears the iphone freeze.
Never the less i can access the recovery mode and dfü mode, but i can't restore it because i need the current firmware version and i didn't saved the shsh bloob or made a backup in itunes. Can somebody please help me with this issue.
I just need to delete the problematic app or a way to restore the iphone to 4.2.1.
The iphone was jailbreaked with greenpoisen and redsnow.

Maybe i can transmit an patch with an exploit and execute it so the app will be deleted.

What app was it you installed? Were they all legitimately purchased from the App Store or Cydia, or were they free apps from Cydia? Want to make sure there isn't anything that would be patching the phone's installer....