Hi Dan.
I start FSX with a Default FSX Aircraft and when that is my home Airport which is YWOL, I then change to a pre loaded saved PMDG either the 800 series or at this time the 900 series, the 800 aircraft are downloaded from the installation CD and the 900 aircraft using the operations Center.
I had downloaded a Qantas Airlines PMDG, 737-800 WL aircraft did a flight with this then saved the aircraft in the FSX / Flights section and followed the same procedure as above to reload the pre-saved aircraft but the second time it will not initialise, as I mentioned before the PMDG 737-800 WL in the House Livery initialises every time.
I have noticed in the Cockpit view that when selecting the overhead panel it shows that the Cowl Valve is open, hope this is enough information, I attempted to attach 2 screen shots but was not successful.
Jacob Mulder