Some of my games wont save...

Few days ago I got my R4 SDHC card with 8Gb microSD(SanDisk or soemthing like that).
I downloaded the latest Kernel from their homepage Here.
I added a Pokemon skin(YaY pokemon!) and than moved the fiels onto my microSD card. There were 7 files.
Than I made a Games folder and put in about 30 games(1,6GB).
It worked great and played some games.
But next day when I wanted to play Profesor Layton its said that thw file was corrupted and it deleted it.
Same problem at Pokemon Platinum and Mario and Luigi - Partners in Time.
Another problem is New Super Mario Bros. First is said that all files were corrupted and deleted them.
After that its said that the third one is still corrupted and it keeps spamming that.
Help please
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Anyone maybe.