curious curious because I have all versions of Wings!
Your 0.99.02 and 0.99.04 (the last! )
Maybe Seems there is something with the name of the file
in your folder, "TestFBXWeld1.fbx" appears in the wings selection windows, but when I troncate it the .fbx, it's appears TestFBXWeld1 in the window selection and TestFBXWeld1.fbx in the wings3D message error
as you had writed in fact TestFBXWeld1.fbx.fbx ???
but even with that, that's is "Unable to read the file"
and more curious I had loaded your first FBX test in the past with success!