That explains everything - your guess is right on the dot. If you can figure out what your hardware variant code is, use whatever you tried to change your product code with to set it to xxxx00 (where xxxx is the HW variant). If you flash back to PR1.1 you might be able to figure out which HW variant your phone is using sysinfoclient -a. This is why changing the product code is ill-advised - remember, there's no need to do so before flashing!