SVG on firefox, the linux way

I stumbled upon the SVG issue described here[1] and there[2], but I didn't found an answer yet.

Let's take this wonderful tutorial of `<set />` based animations from peter's website[3].
(put your mouse over the green square to fade the blue one, full page here[4]).

It works perfectly, as you may see. Saved on disk and opened with Firefox, locally, it fails on Linux (seems to work on windows) !

You can try it at home... 
Any clue on what's missing ?

tested on ubuntu oneiric with firefox 11.0 and winXP with the same firefox

  [1]: http://doctype.com/firefox-linux-svg-support
  [2]: http://stackoverflow.com/questions/6186335/how-to-display-interactive-svg-in-a-window-on-linux
  [3]: http://www.petercollingridge.co.uk/sites/files/peter/hover3_set_attribute.svg
  [4]: http://www.petercollingridge.co.uk/data-visualisation/mouseover-effects-svgs