Well, tried a friend's 256mb graphics card and temporarily added another gig of memory...still the SAME problems with all the default 747's and Bombardiers...no change at any / all settings. Guess I'll have to invest in a 512mb card, another 2 gig of memory and uninstal / re-instal again and see what happens from there. In the mean time, I'll just fly all the other aircraft that work fine in FSX. Hopefully this is not a "bug" in FSX.
Nigel