On turn 70. Since then, I ran the file validation option at Steam and it has been working fine ever since.
There is nothing wrong with my system that I am aware of, however, if I check the file validation, it many times seems to say that the validation has failed. This is not unique to GC3, either. It happens with most of the games I play from Steam.
I don't know what make of that.
Thank you for your attention,