Can't restore my Wii: BootMii Won't Work
To get bootmii to work you must first install it with letterbomb. To do this go into the letters section of your wii locate the letterbomb (it is red and has a bomb sticking out of it) when you open it select the bootmii installer (It should be under the homebrew channel) Next time you open bootmii from the home brew channel it should load properly and not get stuck on a black screen. Note the wii controller will stop working this is normal you can use the buttons on the wii console to navigate the options. After you settup bootmii the controllers will work again.
Also if you have started bootmii before installing it from letter bomb and you are stuck on a black screen it is safe to turn of your wii.