I conducted further testing:
I started a new standalone scenario, 'Act of War, 1968' and saved, then exited. Re-loaded fine without the error. Also started a new 'Shamal' scenario with this build, 1139.2, ran it for a bit, saved, then re-loaded without error.
So, I suspect my problems were all related to that earlier build.
"I say again, expend ALL remaining in my perimeter!" - Platoon
"This is JB27, on target...fire for effect.." - Me