 <p>That error occurs after a fatal error ( anywhere ), but I think it happens only in older versions of Kohana3. Delete your cookies after this occurs.</p> <p>Try downloading the <a href="http://kohanaframework.org/download/kohana-latest" rel="nofollow noreferrer">latest version of Kohana 3 again</a></p> <p>EDIT:</p> <p>You can get more info on this bug <a href="http://forum.kohanaframework.org/comments.php?DiscussionID=4606&amp;Focus=34920" rel="nofollow noreferrer">here</a></p>