Temporary Nintendo Network Maintenance

Nintendo will be holding a temporary maintenance on their network from (approx.) Tuesday, 4 December 2012 18:00 to Wednesday, 5 December 2012 03:00, a quote from their website:

Affected services:
Wii U
Nintendo eShop
Nintendo 3DS
Nintendo eShop
Wii
Wii Shop Channel
Nintendo DS
Nintendo DSi Shop

*Some of the affected services’ features are not available during temporary
maintenance. We thank you for your understanding and apologise for any
inconvenience.

Source