I've been having an issue with FSX crashing when it gets to 100 per cent for a couple of months. It'll load as fast as normal, but sometimes when it gets to 100 per cent is just crashes. The little blue circle comes up (hourglass for XP) and it just dies.
Try disabling your AI. You could have had installed a bad AI file, and those can crash FSX.
What addons have you installed? If any, start uninstalling them in reverse order, and see which causes the crash. If that doesn't work, try with different airplanes and different settings until you figure it out... Or you could just reinstall, which you may end up having to do anyway.
Delete the log file and see if that does it.
If not delete the fsx.cfg, the Sim will build a new one.
Hope this does it.
Have you tried uninstalling and reinstalling yet ❓