Dragon Ball Z: Budokai 3

I bought this game used on amazon, and it had no scratches and worked fine.
I bought a 8gb memory card fro a seller named e-stop on Amazon, and it seemed to work fine. Yesterday, after i exited the Capsule shop and it saved my game sucessfully, it froze. I reset it and the data was corrupt. I made a new file today, and after i saved and exited Goku's DU. i turned the system off. When i went to load my file it said it was corrupt again.

Anyone know why? Is it the system, memory card, or the disc?