You give your feed URL at
http://www.telerama.fr/rss/services/podcast_musiques.xml.php?flux=MusiquesPodcas t
which at a quick look seems to be OK. However the URL iTunes is looking for is
http://www.telerama.fr/rss/services/podcast_musiques.xml
There is a 302 redirect on the server from this to the URL you give, which works in a browser but does not work when subscribing manually. (In fact though it's difficult to analyze it looks as if it is a double redirect - in other words there is an intermediate URL, which may be the problem. This intermediate URL appears to be
http://logi3.xiti.com/get/podcast.xml?xts=80368&type=Podcast&flux=MusiquesPodcas t&url=http://www.telerama.fr/rss/services/podcast_musiques.xml.php?flux=Musiques Podcast