If when you try to change the product code, the Nextgen client just freezes and then when you disconect, it says it can not identify the phone, please follow the following to roll back to the older Nokia USB drivers on your PC
First, remove all previous Nokia programs (Nemesis Service Suite, Nokia PC Suite, Nokia Software Update, PC Connectivity Solution, Cable Drivers, Nokia Modem Drivers, etc.). from "add remove programs in control panel, then Restart your computer
After that, install older version of Nokia PC Suite from http://nds1.nokia.com/files/support/global/phones/software/Nokia_PC_Suite_682_rel_22_0_eng_us_web.msi as this only works with OLDER DRIVERS !!!
if it ask a new version available on internet during or after installation, do not update Nokia PC Suite from internet before. (And don’t re-install Nokia Software Updater).
Then repeat the change product code with Nextgen Client