For People (like me) who got previously
"Unable to mount SD Card" OR "TAFN3DS sd card áb áb áb áb áb áb áb áb" OR just white freeze.
And ONLY for people (like me) who use a SD 2GB Sandisk (Normal/Ultra II) or less (To keep Original Nintendo DSi BIOS)
Here is finally a solution :
Do NOT use any SD Formater software it will NOT work at all on a Sandisk Ultra II 2GB (i tried a lot of them with no luck).
Code:
0) Backup every files of the SD Card
1) Use win32diskImager and read all bytes of the SD Card to a file
2) Use hxDwD and fill with 00 every hex values
3) Use win32diskImager and write all bytes from the file to the SD Card
4) Delete the primary partition under diskpart (cmd) or Computer Management
5) Launch again diskpart from the cmd
6) Type command : List drive
7) Type command : select drive 3 (if the SD card is 3)
8) Type command : clean
9) Type command : create primary partition
10) Format the SD Card with Windows to FAT32 Cluster 16Ko (yes 16ko not anything else) (Full erase) (NOT using a SD Tool => will not works with 2GB Sandisk Ultra 2)
11) Copy all backuped files back into the SD
12) Now GBARUNNER2 is no longuer display error or freeze !!!!!!
Now any 512mo, 1GB, 2GB SD Card will works fine


(unless they were compatible with the DSI/3DS before).