The problem may be a combination of the game being too scratched up in the particular area on the disc where that data is and the old memory card. You may have to start again, I'm afraid.
Also, if the disc is seriously scratched up you may want to look for a place in your area that repairs discs. The fee for this is normally somewhat small and it will bring your disc back to like-new condition. You should be able to find this service at local game stores or places that sell used CDs.