Hi
I have the same problem after upgrading to WordPress 3.5! Plus, adding hyperlinks into posts or pages was a problem too!
I’ve added define(‘SCRIPT_DEBUG’, true); in wp-config.php file, but that resolved only the switching between html and visual editors problem…
BUT, I’ve installed “All-in-One Event Calendar Plugin” version 1.9.2 from their site, and the problems are gone! I still have Kino Events Calendar installed and working OK.
The only problem is that I have two calendar plugins running but I use only KINO one :)))
Also, on Kino Events Calendar, Tooltip text on Event Hover is not styled. To fix this I’ve commented lines 1134-1143 in “kino-events-plugin-folder/js/calendar.js.
Hope this works for you too, cause at least solves the problems temporarily, so you find better option or wait maybe for Kino Events plugin update.
Cheers,
Kole