you have to restart picard to activate the change on "preferred release countries".

on this acoustid http://acoustid.org/track/cee7d9e5-50c5-4f3a-bf08-d5160a35f62a,
if there's no countries preferred, you have 2 english albums (compilations, but that's not the pblm)
if you set "french" and scan again, the english albums are still choosen
you have to restart picard to make active your change and have the french compilation "NJR music awards 2007"