Couldn't get media info for input file (invalid image/video?)

I can't seem to get the script to work. The following error

`Couldn't get media info for input file "video.mp4" (invalid image/video?)`

Appears even when running the test suite script, and none of the examples produce any new files. I've added the latest versions of ffmpeg and ffprobe to the PATH but to no avail.

Windows 7 x64.