Win 10 x64 / nVidia GTX 780 with latest drivers

Blender Version
Broken: 2.78.4 Hash: 411836d
Worked: Official 2.78a

FBX import works as expected but as soon as I try to import the same FBX or a different one Blender throws this error:

`Traceback (most recent call last):

File "H:\blender-git\build\bin\Release\2.78\scripts\addons\io_scene_fbx\import_fbx.py", line 2252, in load
  elem_root, version = parse_fbx.parse(filepath)
File "H:\blender-git\build\bin\Release\2.78\scripts\addons\io_scene_fbx\parse_fbx.py", line 184, in parse
  init_version(fbx_version)
File "H:\blender-git\build\bin\Release\2.78\scripts\addons\io_scene_fbx\parse_fbx.py", line 111, in init_version
  assert(_BLOCK_SENTINEL_LENGTH == ...)

AssertionError`

Repro steps:

• Open Blender
• Import > FBX any FBX you like (a simple cube does the trick). The source of the FBX doesn't matter. Even FBX exported from Blender cause the issue
• Everything should work and the geometry is imported
• Repeat the very same and import the same (or a different) FBX
• Blender throws an error and doesn't import anything
• You will have to restart Blender to get the importer working again.