Hi Ken,
Apparently, not so long a shot, for there were indeed double backslashes in config.php (Am at a loss as to how they got there). Going back to 1.5.2 might cause other problems for us, because we upgraded our database and PHP versions for a (failed) upgrade to 1.6.1. and Moodle 1.5. does not co-exist happily with those newer versions. We must hope that our problems with 1.6.x will be hammered out soon (including the upgrading of the contrib modules we use (Mail, Userdir/returnfolder and Netpublish), so that continuity is assured.
Rgrds,
Paul.