Vimeo embedded video cannot be played in Firefox

Here is my config:
- Mac 10.9
- Firefox 28-29

My iframe containing the Vimeo video stays black and displays this error message:
< This video can't be played with your current setup. >
It works fine in all the other browsers.

enter image description here

Markup iframe:  
<iframe src="//player.vimeo.com/video/83913899?title=0&amp;byline=0&amp;portrait=0&amp;color=111" width="960" height="540" frameborder="0" allowfullscreen="0" kwframeid="1"></iframe>

Link to page:
http://www.monakimprojects.com/projects/uniqlo-campaign#slide-02

PS : A friend told me it works fine for Firefox 29, Mac OS X 10.6.
So it looks like it is an OSX problem.

Solution

VIMEO support answered :

You need to have flash installed to watch Vimeo videos in Firefox on OS X because they don't support h.264 playback.

Ah hum yes ok I just reinstalled my Mac a few days ago thats why...
But could they make their message more precise no?

Instead of a silly joke and

This video cannot be played with the current setup

I would have prefer

This video needs flash player installed to be played

Agree VIMEO team?
Thx.