I had the same error on my r4 sdhc. Unsuppoerted DLDI. I managed to run Pokemon Black 2 using MAIO multiflashcart update 9.xx and
Moonshell2.05 - MAIOs YS Loader Mod. Inside the multiflash update there are flash cart update for different types of flash carts (such as r4i ,r4 sdhc, acekard and so on). There is a trick to installing it though.
This is what you have to do. ------
First copy the relevant MAIO flashcart update from the folder "MAIO Multi Flashcart Update 9.xx" to the
root of your Micro sd card. For me it was R4 SDHC
Then copy the contents of "Moonshell2.05 - MAIOs YS Loader Mod" to the Micro SD card.
Then copy the following from the official firmware released from your DS flashcart's website.
R4iMenu folder
And possibly all the DAT files
copied the following Dat files to my Micro Sd card and it worked
_DS_MENU.DAT
R4.DAT
TTMenu.dat --- copying this seems to be not necessary