Our mediawiki was installed December 2006 on Mandrake 10 from a manual mediawiki 1.5.2 php 4.3.8 mysql 4.0.20
June 2009: updated to Centos 5.3 mediawiki 14.0 mysql 5.0.45 php 5.1.6 The weird things needed were:
chmod 733 /var/lib/php chgrp wwwserv /var/lib/php/sessions
in addition to the ever so confusion having to set the super user button in the form, despite that we use the special root's password for mysql. Also needed to reset the $wgEmailConfirmToEdit = true; otherwise anybody can edit pages.