After I did the update on dec. 10th 2013, over which I linked my Wii U with my 3DS and the nintendo account as well, everything worked fine, Miiverse functions were ok at first try. During the process of update, I chose to use my account Mii instead of keeping my 3DS Mii so I can have the same no matter where I am. I'm sure many of you did the exact same procedure with the exact same results. But have you tried Super Mario 3D Land ?
I started Super Mario 3D Land and found my savefile had disappeared. But I also saw the two little stars on top of the save file I used. I created a new game on that savefile fearing I lost all my progress, using my Mii, on that savefile. The progress wasn't lost so I played a bit. I then closed the game, played something else and came back to Super Mario 3D Land. When I got into file selection screen, I found my savefile disappeared again with the two stars on top, again. I decided to create the savefile with another Mii I had created. After playing, quitting and restarting the game, when I got into file selection screen, everything was OK. I suspected a glitch in some register, so I changed back the Mii assigned to this savefile that was now visible to my original Mii. The problem came back. The only way of having a visible save file when on file selection screen is to assign my game to another Mii. I even tried to download the official linked Mii I had on my Wii U to create a copy on my 3DS and used it for my Super Mario 3D Land as a copy, the problem remained. Very weird...
This is not a major bug since no data is lost but this is certainly disappointing for an update... which is by definition supposed to enhance, not the opposite.
Am I the only one having this issue, and if possible, any solutions apart from trying to format my console ?