Just tried on windows 7, 8.1, and 10, it doesnt matter where i have the fbx it works fine for me, i even tried it from a usb stick.
I did have a similar idsue a few versions back when lee did the fbx ground work, but that turned out to be my fbx files and not GG, at the time GG just didnt like one of the two fbx formats blender ecmxports, cant remember which but its one of the two versions if fbx 2010.
Primary Desktop:
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
Secondary Desktop:
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
Laptop:
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.