(The same issue affects the multilang filter itself).

This seemed to make it work:

Index: multilangupgrade.php
===================================================================
RCS file: /cvsroot/moodle/moodle/admin/multilangupgrade.php,v
retrieving revision 1.4
diff -c -r1.4 multilangupgrade.php
*** multilangupgrade.php 15 Jun 2007 06:08:51 -0000 1.4
--- multilangupgrade.php 18 Jun 2007 08:41:03 -0000
***************
*** 59,65 ****
                  if ($rs and $rs->RecordCount() > 0) {
                      while (!$rs->EOF) {
                          $text = $rs->fields[$column];
! $search = '/(<(?:lang|span) lang="[a-zA-Z0-9_-]*".*?>.+?<\/(?:lang|span)>)(\s*<(?:lang|span) lang="[a-zA-Z0-9_-]*".*?>.+?<\/(?:lang|span)>)+/is';
                          $newtext = preg_replace_callback($search, 'multilangupgrade_impl', $text);
                          if ($newtext != $text) {
                              $newtext = addslashes($newtext);
--- 59,65 ----
                  if ($rs and $rs->RecordCount() > 0) {
                      while (!$rs->EOF) {
                          $text = $rs->fields[$column];
! $search = '/(<(?:lang|span) lang="[a-zA-Z0-9_-]*".*?>.+?<\/(?:lang|span)>)/is';
                          $newtext = preg_replace_callback($search, 'multilangupgrade_impl', $text);
                          if ($newtext != $text) {
                              $newtext = addslashes($newtext);