When you tried different drivers, did you run Driver Sweeper after uninstalling the drivers?
Thanks for bringing this program to my attention, as it seems to have done the job for both games.
I ran it and tried several different drivers, using it to clean out the left over bits each time, and finally got it to work with the 10.5 drivers. So it seems there was a corrupt file or something from an older driver and an incompatibility with the newest one that was causing my problems.
Thanks again for the other suggestions people gave as well.