tales of phantasia save corrupt

[gbarom]

I had recently downloaded the gba emulater visual boy advance and the game tales of phantasia US rom. I had been playing and made it through have way into the game. All of sudden, I open my emulator and I wanted to load hard played game and I discover that the rom as the menu says is corrupt and must be overwritten. I had restarted the game, and again, i saved, and I got the same message!
What is happening and how can I fix it?
thanks