http://www.iphone4idiots.com shows how simple it is to upgrade your iPhone 4 firmware to 4.1 using Tiny Umbrella thus keeping your baseband at 01.59.00. This will allow you to jailbreak with Greenpois0n or Limera1n and then be able to unlock. If you don't use Tiny Umbrella you can still jailbreak, but might never be able to unlock your iPhone as it will upgrade your baseband. See the website for full step by step how to guide. You can download Tiny Umbrella at http://thefirmwareumbrella.blogspot.com/ and download 4.1 firmware at http://www.iphone-hacks.com/iphone-downloads/file/252
