I am having the same issue, tried deleting the PMDG files out of Appdata and SimObjects then re installing, nothing works. Keep getting that message on both my PMDG 777 and 737ngx

 

Please sign your name to your posts and if there is a problem after the re-install of everything, send us a ticket at support.precisionmanuals.com

The error I had was that whenever I selected any PMDG aircraft from the FSX 'Select Aircraft' screen, the 20 second initialization countdown would not engage.  Thus, all of my cockpit views were skewed and out of focus, and none of my gauges, switches, buttons, or FMC would function.  I emailed PMDG and sent them the fix that I applied to all PMDG models.  They told me that the fix would not make any difference at all, however, after about two months of not being able to fly any PMDG aircraft, (after paying ($70.00), I was able to discover it after many sleepless nights of experimenting.  After I installed this change, I haven't had a single problem for over a month.  PMDG sent me several suggestions, but none of them worked.  The fix is this:

1.  Go to main FSX file

2.  Go to SimObjects

3.  Go to Airplanes

4.  Go to any PMDG aircraft file

5.  Under [General] erase atc_BOEING because it is already listed under [fltsim.0]

6.  Under [General] erase atc_model=B738 because there is a conflicting line under [fltsim.0] which reads atc_model=737-800 (or whatever is listed there)