My DS is becoming more and more unstable.

I recently installed YSMenu using an automatic tool I found on GBATemp on my M3 Simply. My DS has become very unstable, it often does not boot up and I am left staring at a black screen. Other times, I will get the initial DS Boot Up sequence and it will crash then. And if I am able to access my M3 Simply with YSMenu firmware. My DS will lock-up during a game. So far it has only locked up whilst attempting to play COP The Recruit and Star Wars Battlefront Elite Squadron, it always locks up while playing these. It rarely locks up when playing Modern Warfare Mobilized and Bowser's Inside Story.
Any tips on how to stop this? Or reasons on WHY it does this?

 

Maybe its your MicroSD's problem?
Try backing up all the files on the MicroSD and reformat the MicroSD.

 

Do you recommend a certain format?

 

I set it to FAT32 (Or something,can't remember) but you might want to wait for a mod to confirm this.

 

Click left on your micro sdcard letter drive it is using and see on the list format, then format it in fat 32, simple!