My Wii U crashes if I enter with a non-pretendo account

[storm ice]

This also happened to me lol, you can only play games with the Pretendo network, if you want to use other apps, you have to go back to the Nintendo network, which is by pressing L+ down arrow + minus button.

Then go into inkay, and set Pretendo's network to false, and you should not have this issue when you're in Nintendo's network.

And as you might already know, if you want to play online games, just set the Pretendo network to true