Some of you might have noticed the annoying 1604, 1600 error when restoring to iOS 4 custom firmware in iTunes which is built using PwnageTool 4.0 /4.0.1 or sn0wbreeze v1.6. The error in question looks something on the lines of this.

Well, the only solution we could find for this problem is one posted by Carlos leopoldo on the Redmondpie,which  goes something like this:

Steps to fixing 1604/1600 iPhone restore error:

• There is no need to reinstall iTunes. Keep the same version that you have used to restore or backup previously.
• Make sure that iPhone is disconnected from your computer and that iTunes is closed.
• (The following step of fixing 1604 iPhone restore error is Windows specific, if you are a Mac user, you may have to locate the folders yourselves as I am not sure) Go to the folder C:\Documents and Settings\<username you use to login to windows>\Application Data\Apple Computer\iTunes\iPhone Software Updates.
• You will see one or more files. Cut and paste them somewhere else. Do not delete them in case the steps does not work for you, you can still copy them back to the folder. You can find out your username by doing a Ctrl-Alt-Del. If somehow you cannot find the folder, you are probably in the wrong user directory.
• Launch iTunes and put your iPhone in recovery mode. Refer to this article on Unable To Restore iPhone on how to do put iPhone in recovery mode.
• Proceed with restore and iTunes will download the update online. If you are downgrading to a lower version, do step 3 and leaving only the firmware file that you want to downgrade to. Double click on the file and iTunes will begin the restore.

please do remember to comment if this fix works for you.

[via redmondpie]