The reason is, that qTranslate does not add a filter site_url for transforming urls.
Please be aware, that bloginfo_url and site_url refer to two different things in wordpress: difference-between-get-bloginfourl-and-get-site-url.
in qtranslate_hooks.php into
add_filter('bloginfo_url', 'qtrans_convertBlogInfoURL',10,2); add_filter('site_url', 'qtrans_convertURL',10,1);
This is doing the trick and in my installation it works without any issues so far.
I would be glad if you could implement this.
Thanks for the great plugin