When auth.phtml is run, the $userinfo[givenname][0]
var is not registrerd for others than anonmymous
users.
Simplest way of dealing with this is to add the
following line just before the first if (!
$anonymous) statement.
if ( strlen($userinfo["givenname"][0]) < 1 ) $userinfo
["givenname"][0] = $username;