I created a sprite Pivot animation, now when I try to open it, it says, " invalid point operation"?

When i do an animation i put a sprite in it and save it, but next time i open it, it say invalid point operation. I see that the file extension is .piv. It is loading all animations that don't have a sprite. I save my sprites as 24 bitmap, but as a Jpeg,it wont count as a sprite. Same thing with the other options.