Hi Paul,
that issue as far as I know resides within FSX itself, all I can say is do you have an upto date UIAutomation.DLL....it could also be a scenery issue as some scenery can cause FSX to crash,i know some users have had to disable or remove some scenery to prevent this...maybe a graphics glitch including Direct x-rerun Direct x9C again or type DXDIAG in RUN from your start menu and check your system that way.
Also try PMDG forum incase that issue has been reported before,try this and report back please with any solutions.
You could make sure any runtimes are installed correctly from front of this forum/website see FAQ's..also validate your files on options#2 screen.
Also run the cumulative updates again,just run and let it overwrite existing files,no need to uninstall anything.
Try this for now and let us know how you get on,