Hi
@drenco, try with FW4 K1.04e from the offical web (and if this is the one you are using, try with the last Release Candidate Firmware-Kernel from
#405 comment). Somethings to add, microSD formated FAT32 32KB Cluster, try with just few games in the microSD card, see if the "SAVER" folder is already created, if no, create it in the Root of the microSD and if you can use a save created with the other console. (When mixing saves, ALWAYS use the same FW&Kernel with the one it was created). If your screen has brightness level control, turn it all the way down.
Also, can you confirm your GBA can play perfectly original GB-GBC games? Because with a couple of friends I had an issue (GBA SP 001 & GBA Normal Indigo) those consoles were like weird only from the logic that plays GB-GBC games, beacuse they both play flawlessly GBA games (Even the EZ Flash Omega), so the EZ Flash Junior was working very weird when loading them, like sounding correct but displaying all kind of weird numbers and symbols of a corrupted signal.
If it still doesn't work, maybe it's an issue with the power because of the modification :s ,but let's wait to see if another mate can make any other suggestion. Cheers.