As in title users Just can't get the like button to work properly on my site. When they click, at first the button seems to work but it soon gets "unclicked/not liked".
The problem was related to a Joomla Component (System Language) which were passing the wrong url to the Facebook Like Button, adding to it the language code suffix.
When facebook tried to fetch the url a 404 error were given so the button weren't working. Once disabled the Language plugin the button started working correctly.