Apple has released the iOS 4.1 which features a new baseband 2.10.4. If you update to iOS 4.1, you will lose the jailbreak and unlock.Update iPhone 4 to iOS 4.1 Without Baseband Upgrade The latest Ultrasn0w 1.1-1 nor the downgrading back to iOS 4.0.x (with SHSH blobs) will not be able to unlock the iPhone 4. Notcom has found a way to upgrade to iOS 4.1 without upgrading the baseband to 2.10.4 and allowing you to unlock the iPhone 4 on iOS 4.1 as soon as the jailbreak for it is released.

Here is a simple step by step guide  to update iOS 4.1 while preserving the 1.59.00 baseband:

  1. Terminate all working applications.
  2. Download the latest version of TinyUmbrella (4.1.3) from here( Mac/ Windows/Linux) and launch it.
  3. Download the iOS 4.1 from here.
  4. Press the ” Start TSS Server” button
  5. After that launch iTunes and press restore (Not Update) your iPhone 4 to stock iOS 4.1. To do this, press and hold Left “Shift” button on Windows (left “alt” button on Mac) on the keyboard and then click on “Restore” (Not “Update” or “Check for Update”) button in the iTunes  and then release this button.
  6. Now iTunes you the location select the location for your downloaded firmware file. Select that ipsw file and click on “Open”.
  7. iTunes will show 1004 error (baseband update failed). You do not have to worry because it’s part of the plan.
  8. Click on “Kick Device Out of Recovery” to bring your iPhone back from the recovery mode.
  9. Restart your iPhone 4.

It’s done. Be surprised to find your iPhone 4 working on iOS 4.1 with the old baseband 1.59.00!