Apple recently released the new version of the firmware. The latest version is 3.1.2 and is unlockable via PwnageTool v3.1.4.
Do not try to update the iPhone with these firmwares, else you’ll loose unlock. Use PwnageTool to create a custom ipsw using these firmwares, the upgrade your iPhone using the new custom ipsw files.
Here are the direct download links for iPhone 3.1.2 firmware:
iPhone 3GS: Download
iPhone 3G: Download
iPhone 2G: Download
Enjoy 
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[...] your iPhone to new 3.1.2 firmware directly using iTunes or by using the direct download links and using shift+restore on [...]
Thanks for the comment. I have a question about the update:
Upgrading to 3.1.2 via Itunes in my Powerbook (with the Iphone connected) brings up the usual apple Window, saying that there is a software upgrade to 3.1.2 available. Choosing that, the window you mentioned comes up: Itunes will update your phone and check the upgrade with Apple. Now, did you mean that this way to upgrade is recommended or will I loose unlock using this upgrade? Thanks so much again
Thanks for the comment. I have a question about the update:
Upgrading to 3.1.2 via Itunes in my Powerbook (with the Iphone connected) brings up the usual apple Window, saying that there is a software upgrade to 3.1.2 available. Choosing that, the window you mentioned comes up: Itunes will update your phone and check the upgrade with Apple. Now, did you mean that this way to upgrade is recommended or will I loose unlock using this way to upgrade? Thanks so much again
[...] Step 4: Download 3.1.2 iPhone and iPod firmware from here: http://www.technonix.com/2009/10/iphone-3-1-2-firmware-direct-download-links/ [...]
i downloaded it for my 2g iphone, but after i ran this software, my iphone is modem firmware is still 04.05.04_G. why? does that mean i am not able to unlock my iphone no more? thank you in advance
[...] 1. Download iPhone 3.1.2 firmware using direct download links posted here. [...]
i downloaded the snowbreeze app. and the downgrade file… but i cant find the .ipsw file… snowbreeze can not reconize the file to continue … what did i do wrong ?
I am using and iphone 3g firmware 3.01 and i want to update it to 3.12 too many people have problems and if i in-counter a problem too can i just go back to 3.01 without loosing any thing ?? thanks in advance
I have a 3.0.1 iphone 3gs that is jailbroken. Can I upgrade to 4.0.
is it compulsery to upgrade before we jailbreak ipod touch 3G and iphone 3GS