Are you running the slideshow as local files?
If so, the URL in the address bar starts with "file:" instead
of "http:"
For security reasons, some browsers disallow this.
You may have to push your entire slideshow to a remote server.
Or access it locally via a locally installed web server.
Hint:
In Firefox, you can use local files if you change the option
"privacy.file_unique_origin" to false in about:config.
Don't forget to change it back afterwards!