These paths... The SDK installation assumes that you will take the default side-by-side installation path. If you tell the SDK to install in a non-default folder (mine is D:\FSX SDK and FSX is in D:\FSX Flight Simulator), the installer will still give you the side-by-side relative paths. Changing them to the hard-coded real path solves this problem.<Path>..\Microsoft Flight Simulator X SDK\SDK\Environment Kit\Traffic Toolbox SDK\traffictoolbox.dll</Path>
[Edit] Clarification: Even though the installer was told to use D:\FSX SDK, when I opened up the dll.xml file the SDK installer had still written the default path of (e.g.)
..\Microsoft Flight Simulator X SDK\SDK\Mission Creation Kit\object_placement.dll
instead of the expected
D:\FSX SDK\Mission Creation Kit\object_placement.dll
Poor installer coding.