[dasmoover]

I have used this JB successfully on two 3.2.1 devices. I have received my fourth K3W from Amazon today (3.2.1 576290015).

First attempt: Wifi On - Failed - U007
Second Attempt: Wifi off + renamed documents - Failed - U007
Third Attempt: Place on drive + reboot - Failed - U003
Fourth Attempt: Wifi off + rename documents + renamed system - Successful!

Note: I did NOT need to de-register. Timing is important as well

menu + down*5 + click + menu + down*2 + click*2

Make sure you restart your device after moving the documents and system folder, this will allow your Kindle to regenerate 'clean' system files and remove evidence of your content. I attempted to update after moving the files in the same run, the Kindle refused to acknowledge the existence of the update file (greyed out). After a fresh restart and file transfer it worked.

Thank you for your time and efforts Yifan Lu.

Hopefully this will help someone struggling (First device took over 20+ tries to get it right, but it works, I do not think certain Kindles will refuse it)