Originally Posted by silverspear
From what I think, I suspect that amazon indeed has differentiated PW-J and PW-I (international), either through firmware, or by physical hardware like mac address or something. If someone can confirm if amazon does provide different download links/versions for PW-J and PW-I, then we will know if it's by which method.
I don't think it is firmware, but simply the 3G IMEI addresses are not registered with the international providers, so they don't accept them.
No need for firmware or hardware differences.