This problem has only recently risen it's head - whenever I customize graphics, I can open the menu, but without fail closing it again causes the sim to CTD. I think there may be something wrong with my config, as when I change key bindings they don't save upon quit. I'm running MSFS off an external drive, with my config settings on the C: drive, and had been doing so for over a month before I had this problem.

If it helps - I installed MegaScenery Hawaii a couple of days before the problem started. I'm running via Boot Camp on a Mac Pro, ATi X1900.