I have started to get this message when accessing k2 elements.
I have problems displaying selected categories from the dropdown box, screen turns white. This might happen after a save of an article, and when saving and closing the screen turns white.
Basically seems that after i have created or edited an article (not sure this is what triggers it), i cannot move around in k2 anymore cause each selection gives me a blank screen. I have to logout and login again.

This has just started to happen, any ideas where to start checking ?

The message i get is
Call to undefined method K2ModelItemlist::getCategoryTree() in /home/2/s/xxxxxx/www/administrator/components/com_k2/models/items.php on line 205

shown to me by joomla error reporting.