Edit the events-calendar.php file, by replacing the function EventsCalendarINIT() with this:
function EventsCalendarINIT() {
$inadmin = FALSE;
if (function_exists('is_admin')) {
$inadmin = is_admin();
}
else {
$inadmin = strstr($svr_uri, 'wp-admin');
}
if (!$inadmin) {
wp_enqueue_script('jquerybgiframe', '/wp-content/plugins/events-calendar/js/jquery.bgiframe.js', array('jquery'), '2.1');
wp_enqueue_script('jquerydimensions', '/wp-content/plugins/events-calendar/js/jquery.dimensions.js', array('jquery'), '1.0b2');
wp_enqueue_script('jquerytooltip', '/wp-content/plugins/events-calendar/js/jquery.tooltip.min.js', array('jquery'), '1.3');
wp_enqueue_script('thickbox');
}
// Always register both the widget and widget control objects
// in case there are dependencies between the two.
$widget = new EC_Widget();
$management = new EC_Management();
register_sidebar_widget(__('Events Calendar','events-calendar'), array(&$widget, 'display'));
register_widget_control(__('Events Calendar','events-calendar'), array(&$management, 'widgetControl'));
}
Found in the plugin bug tracker here:
http://tracker.wp-eventscalendar.com/view.php?id=79