HI guys, just wanted to share how I solved this problem. After I used the latest version of WinPwn (2.0.4) I got the same 1604 error with the subsequent phone locking up. After trying to restore with Itunes I kept getting the same error 6, which means an unknown error, and it simply seemed like I bricked the phone.
Well what really happens is that in this situation you are simply not being able to put your phone in DFU mode. Even when following all instructions on the web you´ll eventually always end up in normal Restore Mode (which is a different thing). So here´s what I did:
Here you can find the complete Pwning guide as well links to download the files:IClarified Guide
Get Ziphone Here
1-Make sure your Itunes is already Pwned and is detecting your Iphone. (for now ignore when it says that it is in restore mode, but leave the phone connected)
2-Download Ziphone, click Advanced Features and select DFU mode (yes, I know... but Ziphone´s DFU option is the easiest method for now)
3-Click on the Output Log you´ll see the program stuck at "Searching for Iphone"
4-Now you have two choices: Simply restart your phone (holding the power button) or try again the manual DFU mode (hold power and home button until screen goes off then release power button but keep holding the home button)
5-Ignore Itunes until Ziphone finds your phone and puts it on DFU mode.
6-If everything went well your phone´s screen should be black and Itunes should detect your phone in Restore Mode (don´t worry, even though it says restore it´s actually DFU)
7-Click Shift+Restore on Itunes and select your custom firmware (the one you created with WinPwn) and let it roll... no more Error 6.
If this doesn´t work, then Uninstall both itunes and winpwn, restart your pc and reinstall both. After that restart this guide. Just don´t forget to do the Itunes Pwning step first (Ipwner option on WinPwn).
That´s it! No need to downgrade your Iphone or Itunes as many people are sugesting. You should be done in less than 30minutes...