More experimenting with IBL, and the problem, like so many, apparently is random. I deleted all lights, reloaded my lighting set with an IBL, and this time the IBL is not directional.

It would be convenient to think I imagined all this. I spent a half hour confirming it, and now I've gone through the exact same steps to replicate the problem, and it isn't happening. This may be the most unstable boxed software I've ever purchased.

M