This is what I have done:

1) Using FSC 9, I created a route without SID or STAR and saved it as a Flight Simulator X Plan (.PLN).
2) I loaded the route into the FMC using SEND > FLTSIM PLN > Scrolling to find my plan.
3) I then saved that route using SAVE.
4) I can load the .RT into the CDU/FMC, add the SID and STAR and do the flight.

This works fine for me. FSX doesn't have a fatal error resulting in a CTD.