There’s a developing story that Apple has put baseband requirements on iOS 4.2.1 released few days ago. Such baseband check will basically render TinyUmbrella unable to kick your device out of recovery.
Thus, those who care for unlock are advised not to update to iOS 4.2.1.
Do not update to 4.2.1 for the baseband protection. TinyUmbrella is no longer able to kick you out of recovery for that version. TinyUmbrella still works for prior versions and will be able to restore and kick you out of recovery for those versions but 4.2.1 has a baseband version check that will stop your device from booting if your baseband was not updated.
As an iPhone 4 user, it means that you can’t restore to iOS 4.2.1 using the TinyUmbrella anymore. The baseband check will prevent you from doing that. Once you accidentally updated your device to 4.2.1, your only option is to restore to iOS 4.1 again (which is the best choice) or restore to iOS 4.2.1 stock but with a tethered jailbreak.
So for now, if you care for unlock – don’t update to iOS 4.2.1 yet! And always make sure you have your iOS 4.1 SHSH blobs saved. I’ll keep you updated on the workaround of this story, so just stay tuned! [via]