If you got some issues registering your nook outside US using WiFi, the reason is most likely a totally wrong date and time setting. Here's your solution:
1. Get root-access to your nook as explained here:
http://nookdevs.com/Softroot
2. Install Busybox:
http://nookdevs.com/Busybox
3. Set your system time:
Code:
adb shell /data/local/busybox date MMDDhhmmYYYY.ss
Example: if you want to set it to 2010-01-22 13:59:27 you will use
Code:
adb shell /data/local/busybox date 012213592010.27
4. Set your hardware clock using system time (otherwise your setting get lost after reboot):
Code:
adb shell /data/local/busybox hwclock -w
5. Now you should be able to successfully register your nook.
Bye, Dominik