Having this problem too (NTDLL.DLL CTD). Not Overclocking (don't even know how.) constant CTD's just migrated from FSX to P3DV3 this weekend.  Tried installing the newest add-on manager as read in another forum.  Running REX 4 Texture Direct, REX Soft Clouds, ASN SP5, and PMDG 737-700NGX; Would love to complete a flight!

 

Faulting application name: Prepar3D.exe, version: 3.3.5.17625, time stamp: 0x5758bb31

Faulting module name: ntdll.dll, version: 6.3.9600.18233, time stamp: 0x56bb4e1d

Exception code: 0xc0000374

Fault offset: 0x000e6054

Faulting process id: 0x6e4

Faulting application start time: 0x01d1dacfef3f9cf6

Faulting application path: C:\Program Files (x86)\Lockheed Martin\Prepar3D v3\Prepar3D.exe

Faulting module path: C:\WINDOWS\SYSTEM32\ntdll.dll

Report Id: 0e20c9b4-46c5-11e6-bfed-240a64036ec0

Faulting package full name: 

Faulting package-relative application ID: 

There are several probable solutions in the AVSIM CTD Guide.  Since you are not overclocked you can discount that possible solution.  You need to move your p3d.cfg, dll.xml, exe.xml and scenery.cfg to a temporary directory (so you can put them back if the fix does not work).  The P3D and Scenery.cfg will be rebuilt back to the default settings.  P3D now has the dll.xml and exe.xml in the same folder as your p3d.cfg and there may be one in the same folder where your scenery.cfg is located.  So you will have to move the files in both locations.

 

You can also try just moving your p3d.cfg and scenery.cfg and rebuild those.  Try the same flight and if the crashes stop, then the cause was in the p3d.cfg or scenery.cfg.  If the crashes continue, you will have to move the dll.xml's and exe.xml's or disable each entry as shown in pages 13 and 14 of the AVSIM CTD Guide.  If you want to use the PMDG aircraft, then you would have to disable every entry except the one for the PMDG aircraft.

 

Best regards,