...well, scratch my last comment about 3Delight being more efficient.
Got home and did a couple minor adjustments on the teeth maps to get them to show up in the render, no changes to the lights or anything else, and all of a sudden it’s “crash city”.
The really stupid thing was when I did the first render this afternoon I was online at the same time and it completed fine.
This evening, I not only was offline, but pared back as many other processes as I could, and every time the render got to about 98 to 99% complete, it crashed to the desktop.
I cannot believe simply adjusting the specular and ambient colour would cause this.