After installing the latest version I've noticed that I'm getting a lot of URLs without the language code (I got some before, but now the problem seems to me greater, or that is my impression). All the options in the language tab are set to yes, including 'Always use language?'
For example, events/xcentric-scenes-in-the-life-of-mary-shelley instead of en/events/xcentric-scenes-in-the-life-of-mary-shelley . The real URL doesn't have a language parameter ('index.php?option=com_k2&id=1951&view=item'). Notice: I'm also getting the URLs with the language parameter and the site seems to work ok. It may be a problem with robots again...