Thanks for the help, AV8R. Although the initial problem was simple (correct RAM limiting), I was not able to solve this new graphics development: No "live" MFDs or HUD graphics. Both were blank and did not respond to keyboard input. Same in cp/g seat. Also, no option menu inflight, just a kind of translucent quarter page on the left side of the cockpit view. No ability to exit game or mission. Stick and throttle worked fine for flight, but no way to fight or navigate normally, etc.
The only change I am aware of from many previous normal flights is an upgrade in my nvidia drivers to 61.76 from an earlier 50 series. I've not noticed any problems in other games. Still using Win98SE.
Will be out of town for a bit, but will investigate for next month.