swf files work on one server but not another

A site I built has linked swf files on several pages.

They all work fine on the server I use for testing and my personal site, however when I upload the same site files to my clients server the swf(s) won't play and the page title is followed by "Flash Player Install". 

I can go back to the site I first loaded to and they still play fine.

This happens on my computers and the clients.

I am copying the site completely new to both severs from the same source files.

Help please.