Content Error After Fresh Installation

I’m trying the content pipeline tool after a new/fresh install of MonoGame. When I try to import a .X (or any file) I get this error:

Build started 10/15/2015 1:42:49 PM

D:/Archived Projects/source/resources/models/signpost/signpost.x
D:/Archived Projects/source/resources/models/signpost/signpost.x: error: Importer ‘OpenAssetImporter’ had unexpected failure!
Assimp.AssimpException: Error loading unmanaged library from path: Assimp64.dll, see inner exception for details.
The specified module could not be found. (Exception from HRESULT: 0x8007007E) —> System.IO.FileNotFoundException: The specified module could not be found. (Exception from HRESULT: 0x8007007E)

Any thoughts here?