About 5 days ago I started having this problem, before that I could play no problem whatsoever... I tried uninstalling the games and installing them again (forwarding them) but it didn't work. My brother mentioned taking the roms off the SD card, booting the 3DS, and then put in the roms again, but I wanted to see if someone could guide me in the right direction first.
It is worth mentioning that:
- I did check with multiple games
-I didn't install some weird software that messed up my nds games - I can still play 3DS and injected GBA games just fine
- For NDS games I use ndsforwarder
-The 3DS as a whole works fine