So to summarise, on your rig, you had to remove the nvidia card, switching to the built in intel graphics, install the secuirty update, and nvidia drivers, before reinstalling the nvidia card.
my rig both the installs work fine with the nvidia card in place, but the system kps, after installing the updated nvidia webdrivers.
my system is setup as a macpro 5,1. nvidia gtx 285. im currently using the built in mac os x driver.
strange i bet the driver versions are the same, just modifed installer to pass the verison check?