SAV Cannot be read?

I was wondering, sometimes when I download a game, it says "SAV file cannot be read, please reinsert game card" or something along the lines of that. What does that mean, and how can I prevent it?

Update your firmware and the game needs to be ARM7/9 patched. Check out common issues here: https://www.romulation.org/forum/index.php?topic=1462.0

Thanks.