Hacking game screen goes blank on iTouch DS

[Nocturnius]

Hey guys. I had a 2 gig micro sd with my games and saves on it then when i got a 4 gig micro sdhc i transfer all my saves over to it. so like i played final fantasy IV on my new micro sd and when I encounter a battle the screen goes blank. and when i played it on my 2 gig it worked perfectly. Also soma bringer froze on me as well. Any idea what the problem might be? Thanks in advance