[business Blogs] thumb does not show up in post page

hiya !

Oups, something strange in this theme about thumbs (featured immages) : they dont show up in the posts !

they come fine in the featured category on homepage, but once reading the post the image just... disappears !

look :
homepage : http://wordpress-blogs.net/
post page : http://wordpress-blogs.net/niouses/noms-de-domaines/

Help ?