Smithers, I'm very sorry for your problems. Too bad! I don't think anybody has found out where these errors originate. To me they don't appear to be savegame-related, but I don't have any idea about how they're caused.
Reagrding Riven: Give it another chance! It is a great game, might be the most sophisticated one ever made. I enjoyed it very very much. It gave me weeks of challenge and fun!