There's no difference, file names aren't case sensitive.
A 7018 error Is a mesh error, it's usually because you haven't zeroed the global location/rotation/scale, usually when your global location is below zero. Go into global mode, highlight your model and press Ctrl+A and select location, then repeat for rotation/scale. Do this for all meshes in your model, then export it again, it should work now.
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.
