No audio on random firefox streaming of wmv

[Filippo Mariotti]

Hi everybody, I'm new to this list and to linux. I use Fedora 8 and I
face a strange problem with Firefox. Audio works great for local files
and some streaming but when I play particular videos inside Firefox they
are completely mute. To test it below I post 2 example, one of each
kind:

I'm perfectly able to hear audio from 

http://www.raiclicktv.it/raiclickpc/secure/stream.srv?id=3286&idCnt=14632&pagina=1&path=RaiClickWeb^Home^Storie^Storie+nere^BLU+NOTTE


But I can't from

http://www.raiclicktv.it/raiclickpc/secure/stream.srv?id=29256&idCnt=32943&pagina=1&path=RaiClickWeb^Home^Storie^Storie+nere^BLU+NOTTE


Both perfectly behave on windows using internet explorer.
Has anybody met this? Is there a way to understand which is the
difference from the videos above?

Mi Firefox version is 2.0.0.14, my Windows Media Player plug-in is
gecko-mediaplayer 0.6.2.

Many thanks in advance for your time.
Regards

Filippo Mariotti