Chouby on "Polylang sudden fatal error"

I just released Polylang 1.5.3. With this version, you should disable the problematic code by setting:

define('PLL_CACHE_LANGUAGES', false);

in wp-config.php. So there will be no more need to modify the plugin code in the future.
This will remain an option as it slightly decreases the performance of Polylang and works as is for most users.