Using Moodle 2.7dev (Build: 20140110) and Survey 2013121801.
Debug level: developer.
Upon answering questions, getting these error messages:

Warning: Missing argument 3 for mod_survey_userformmanager::next_not_empty_page(), called in moodle\mod\survey\classes\view_userform.class.php on line 142 and defined in moodle\mod\survey\classes\view_userform.class.php on line 159
Notice: Undefined variable: currentpage in moodle\mod\survey\classes\view_userform.class.php on line 171