On the My Moodle page, teacher's view, the questionnaires defined in a given course are listed with a number of responses submitted. However next to the number, the name of a string: [[overviewnumrespvw]] is displayed. It seems to me that the string is simply not defined in the questionnaire.php (en_utf8). On my test site, I have modified the questionnaire.php file by adding the approprite string definition and that has solved the problem..