well it's most likely the game itself that got screwed up over time. though you may be on the right track with the battery. If it's still the original battery saving shouldn't even work by now anyway, since the game is roughly 14 years old here in America. Now I have heard a few times that the battery it if left in too long (meaning way past dead) could actually harm the game itself. I say try and replace the battery. See if that works. If it doesn't, just be happy that you have another original cart that works fine.