I had the same problem but there's just a minor error in html_ouput.php, this is how it should be
add to admin/includes/functions/html_output.php
function tep_draw_pull_multiselect_menu($name, $values, $defaults, $parameters = '') {
$field = '<select multiple name="' . tep_output_string($name) . '"';
if (tep_not_null($parameters)) $field .= ' ' . $parameters;
$field .= '>' . "\n";
if (empty($default) && isset($GLOBALS[$name])) $default = stripslashes($GLOBALS[$name]);
for ($i = 0, $n = sizeof($values); $i < $n; $i++) {
$field .= '<option value="' . tep_output_string($values[$i]['id']) . '"';
if (in_array($values[$i]['id'], $defaults)) {
$field .= ' SELECTED';
}
$field .= '>' . tep_output_string($values[$i]['text'], array('"' => '"', '\'' => '', '<' => '<', '>' => '>')) . '</option>';
}
$field .= '</select>';
return $field;
}
New 
