Blender seems to not want to import a FBX 6100 file. Is there any way I can convert the file, or even better, open it directly from Blender?
Try the Autodesk FBX Converter. Unfortunately it is no longer maintained, but it can converts many file formats, up to FBX 2013 format.
Alternatively, if you know a bit of C++ you can write a simple command-line file converter using the FBX SDK.