Hi,
not totally sure, if this is the correct mailing list. On the Croatian Wikipedia a user reported the following error message:
Fatal error: Call to a member function on a non-object in /usr/local/apache/common/php/User.php on line 29
He tried to create a new account, and typed in name, email and password. But then he got the above error message.
His bug report (in Croatian) is on http://hr.wikipedia.org/wiki/Wikipedia:Bug_reports . If you need me to translate or to put a question there, let me now.
Best regards, Denny Vrandecic