Apple hoped that its new firmware release would brick hacked iPhones, it
appears that the hackers have counter attacked by posting instructions on
how to roll back a recent Apple firmware upgrade that rendered their mobile
Enthusiasts have been developing ways to allow the devices to run unauthorized software and to unlock them so that they can be run on any mobile network. These instructions allow users to remove the bricking upgrade but still use some functions like the phone's iPod and Wi-Fi capabilities. At the moment they do not restore the phone's ability to make calls.
Apparently the hackers have not yet found a way to roll back the firmware used by the iPhone's baseband chip, which is used to make calls.