but when I try to launch them, I got a white loading screen, and... nothing more.
If I try to run gba_bios, I got the Nintendo logo, and nothing more.
some possible solutions:
a) sometimes its the bios, maybe another will help (I used one from emuparadise on n3ds)
b) i had a problem with emerald german version, but english version started fine. Do you have game_config in the root of the sd?
c) are you using new 3ds or o3ds? apparently changing the boot launcher for o3ds could help (earlier posts mentioned something about that)
But gameplay is still slower than the videos shinyquagsire showed in the videos it was playable, I guess it has to be optimized for tubeHax or I have to change the bios.