Certain games freezing on N5

Recently, I have this problem on my N5 card when I load certain games, my DS freezees. What's weird is that all of the games used to work, but now thay don't. Plus, I can't access the cheat menu on the games that freeze, my DS freezes there. Anyway, here is a list of the games that freeze my DS whem I try load them:Polarium
Professor Layton and the Curious Village
Pokemon Mystery Dungeon: Explorers of TimeThanks for your help ;D

back up your microsd and reformat it, then put the games and firmware back on.

Thanks, but that didn't work. Is there anything else I can do? :-[

What firmware version are you using? What brand of MicroSD?