A problem with the normal saves of a game

[ItayBM]

Hi, I have been playing Kingdom Hearts Birth By Sleep Final Mix, and the game is divided to three characters. Each time you finish a character, you reach a save menu, in which you can save your data, and then you can return to that character for extra content-and finishing all three characters adds additional contents.
I have been using save states for a while now, and they work fine, but apparently my save state is corrupted, and I cannot save the game normally now-so I cannot access the after-game content. When I try to save in my most recent save-state (either after finishing the game, or at the last save spot before finishing), it says "Checking the storage media." and doesn't do anything.
I did save my game normally, about halfway through the game, and when I load that save, I can save normally there-but of course, I don't want to play the second half of the game all over again.

does anyone have any idea how to fix my save states so I could save normally?