Apple has sent out a software update which bricks all the iPhones
hacked so that they could use what ever phone company they liked.
The latest update brings the Wi-Fi Music Store to the device, as well as several security fixes and enhanced features, find out more here. However it also turns iPhones that were unlocked to run on cellular networks other than AT&T's into expensive paperweights.
Macworld says that two hacked iPhones in its office did not work after the update was installed. Gizmodo is reporting that both the original SIM cards as well as new SIM cards from AT&T won't work in iPhones that had been activated with the original SIM card, then unlocked from the network.
However those who used software to crack into the iPhone are not having any problems if they still use AT&Ts network card. However any third party software was vanishing when their phones were reactivated.