2DS Black Screen Fix after 10.5 update. May also work on 3DS.
*DO NOT FORMAT OR CHANGE ANY FILES AT THIS TIME*
Insert Your SD Card that is causing the black screen into your PC and back up.
Open SD Card and Continue into "Nintendo 3DS" and First Hex Number folder *My folder name was 74fef61c4eb6fc5597d8f632514f6b5c*
After entering the first Hex folder you will now see you system hex folder, Take note of the name. Double Check to make sure your SD card has been backed up, now format.
Insert the fresh SD card into you 3ds turn it on and let it create the new system folder, turn off the system and eject the card, reinsert your SD into your PC.
Copy your backup to the SD card, make sure to keep a backup, as long as you have this you'll always have your original system if this fails.
Open Your Nintendo 3DS and First Hex folder, you should now have two system folders, your original and the new.
Open the new System Hex Folder and copy the extdata folder, now back up to your original system hex folder and open it.
Paste the extdata folder to your original system hex folder, allow for overwrite, after this is complete back up and delete the New System Hex Folder that was created by the 3DS.
--------------------- MERGED ---------------------------
You have a bad menuhax install. You can reset Home Menu without removing anything else on your SD card.
Simply go to your Nintendo 3DS folder and find the following extdata:
SD://Nintendo 3DS/ID0/ID1/extdata/00000000/0000008f/00000000
(ID0 and ID1 being the folder with the really long string of letters and numbers. If you have emunand setup, be sure to you opened the one that corresponds to your sysnand if emunand and sysnand are not linked)
Delete the contents of the 0000000 folder. (note location of this folder will be different depending on your console's region. I only know the location for USA Home Menu).
This will reset Home Menu completely. You'll have to unwrap all the game icons and restore the icon positions/folders they were in. Folders you created will not be lost though. You just have to move non system icons back into them.
.... your way is a lot easier lol