Well for some reason GBA games don't seem to work on my O3DS with this latest release (I'm not sure they even worked on the previous releases),
Booting from amr9loaderhax. Patched AGB_FIRM installed.
If you are on AuReiNand have you updated to 3.6.1. It seems there's been a few changes around O3DS and how things like GBA games work.