Thanks for your reply. I spent about 2-3 hours this morning, trying various scenarios, and found several things. I did delete the settings.dat file, but nothing changed.
1. A second problem surfaced during my trials... the cockpit screen would freeze at times, and would not respond or move to any key, switch or mouse. However, as with the blue screen, appropriate sounds can be heard, such as the throttle increasing, or inside vs. outside the plane.
2. I worked by changing the Visual Effects, Texture Quality and Anti-aliasing sliders in X-Plane.
3. I uninstalled Maxx FX, SMP and