Not sure if this will help, but give it a try.

After the pre-order site asks you to log in, click on your profile settings in the top right corner of the screen. Under settings my language preference was set to English (UK). When I changed the language setting to English (NA), it spat out the proper code for me.

Like I say, not sure if this will help or not, but it's worth a shot! Good luck. Entering a pre-order code really should have been much simpler than this.