This morning I upgraded some wordpress blogs, where I am also using the qtranslate plugin.
After upgrading to WordPress 3.9 the home page was broken.
Looking into the server logs I quickly found the problem:
PHP Catchable fatal error: Object of class WP_Post could not be converted to string in ../wp-content/plugins/qtranslate/qtranslate_core.php on line 455
I wrote to this quick and dirty patch to have the site back online. If you have a better patch please share !