One thing... I AM NOT RESPONSIBLE FOR ANY BROKEN DEVICES. I have not tested it yet. But if you want to, you have nothing to lose since you are on 4.0.2 with no blobs saved anyways. Step 1: Download the iOS 4.0.1 ipsw. Step 2: Extract it with your preferred program. You may need to rename the firmware file from .ipsw to .zip to do this. Step 3: Open the buildmanifest.plist with a plist editor. Search and replace all – 8A306 with 8A400. Save. Repeat the same with the file restore.plist. Step 4: Download iOS 4.0.2 ipsw and open this with your programs GUI. Do NOT extract it. Just open it with the GUI and leave it open. You must use this exact file and not create a new one. If you have to create a new one for reasons like you are on OS X, then use zip command line not explorer or finder to make the zip. I will assume you are using the original file opened in WinRAR for the rest of this guide. Step 5: Take all the files from the extracted iOS 4.0.1 and drag them over to the iOS 4.0.2 archive window that you have open. Step 6: Delete all the .dmg files that have 002 at the end, leaving only the 001 files left. Step 7: Save the archive, and rename it back to .ipsw if you changed the name to get your program to open it. Step 8: Mac: Using Finder, click on “Go to Folder” menu “Go” and type / etc /. Copy the file “hosts” file on your desktop then open it with Text Edit and at the end of the file add the string: 126.96.36.199 gs.apple.com Always save the file on your desktop and then drag it back into the folder “/ etc” Windows :Go to Start, All Programs, Accessories and click Notepad with the right button, select “Open as Administrator”. Now go to ~ / Windows / system32 / drivers / etcand open the hosts file, adding the end of this line: 188.8.131.52 gs.apple.com Save the file. What this does is send iTunes to Saurik's server so it confuses iTunes when it verifies the firmware. Step 9: Put the device in DFU mode. Make sure it is off and plugged in the computer. Hold the power button until you see the Apple Logo, then hold the home and power button for ten seconds, and release the power button but continue to hold the home button until iTunes recognizes your device in recovery mode. Step 10: Now simply open iTunes and restore the firmware you changed. This is it, you should now be able to restore from a backup, jailbreak and unlock your device on iOS 4.0.1 with JailbreakMe and ultrasn0w. Now you should delete the string from the hosts file. Again, if this does not work, don't blame me. I found this guide floating around the internet. This does not work with any other firmware or device please do not ask if this works for anything but iPhone 4/3GS on iOS 4.0.2. If you DID get this to work, please post proof and answer the poll. If you DIDN'T get this to work, tell me. If many people can't get this to work, I will delete this guide and request closing/removal of this thread. Guess what. The likelihood of this working is actually good. Because currently 1/3 of you have /most likely/ saved your SHSH blobs. XD If you know for sure you or someone else has NOT saved your blobs in Cydia or on TinyUmbrella, and this guide worked, please post here.