Nintendo has issued new system updates for both Nintendo 3DS and Wii U, to solve a number of issues including increased stability for both platforms. Unfortunately the Wii U patch is a whopping 625 MB and according to Nintendo the update will take around an hour to complete. The Nintendo 3DS update is smaller and only takes a fraction of the time to complete.
Nintendo recently commented that Wii U units from January and onwards will ship with the necessary system updates installed. Remains to be seen if this the most recent update is included by then.