Have you checked the version of the Flash Player that is installed in Firefox? Here is a link to do that: http://kb2.adobe.com/cps/155/tn_15507.html Also which OS? Do other Flash files play? Can you watch a video at tv.adobe.com successfully? Is there an extension installed in Firefox that might be blocking it?
Just a bunch of troubleshooting ideas that you might have already done...
Just converted .flv to .swf and works fine now!
Firefox was not doing the movie streaming of Media folder
But now it's ok!
Do You know what I'm doing an interface of a videogame in Catalyst?
Yeahhh Catalyst is the "man"!