Problem when switching between languages

Hi,

my website is in french and english (http://www.nicolas-devillard.fr/clonetest).
There is no problem switching between the 2 languages when you’re on a page (like Contact or About).
There is always a problem when switching in a post (properties to rent or sale): the link is wrong and the page can’t display.

qtranslate use a prefix (en/ and fr/) to name each version of a post, and Qtranslate slug use a translation of the title of the post. It seems there is a conflict between this two things. When I desactivate Qtranslate Slug, the problem disappear.

Thanks for help

ps: I didn’t do anything on the Qt Slug options page. I only use this plugin because you say it fix QT bugs.

http://ww.wp.xz.cn/extend/plugins/qtranslate-slug/