Just as Mallcott mentioned, did you install ALL of the simconnects? I played it safe after installing P3D and installed the 3 simconnects, which would be located here:
[Your Sim Drive]:\Lockheed Martin\Prepar3D v3\redist\Interface
The folders that have the simconnects are:
ESPv1
FSX-RTM
FSX-SP2-XPACK
Try installing these and see if it helps.