Are you sure that this field exists in the table? If not, use this dump to create a clean new table:
DROP TABLE IF EXISTS 4images_users;
CREATE TABLE 4images_users (
user_id mediumint(8) NOT NULL auto_increment,
user_level smallint(6) NOT NULL default '1',
user_name varchar(255) NOT NULL default '',
user_password varchar(255) NOT NULL default '',
user_email varchar(255) NOT NULL default '',
user_showemail tinyint(1) NOT NULL default '0',
user_allowemails tinyint(1) NOT NULL default '1',
user_invisible tinyint(1) NOT NULL default '0',
user_joindate int(11) NOT NULL default '0',
user_activationkey varchar(32) NOT NULL default '',
user_lastaction int(11) NOT NULL default '0',
user_location varchar(255) NOT NULL default '',
user_lastvisit int(11) NOT NULL default '0',
user_comments smallint(6) unsigned NOT NULL default '0',
user_homepage varchar(255) NOT NULL default '',
user_icq varchar(20) NOT NULL default '',
PRIMARY KEY (user_id),
KEY user_lastaction (user_lastaction),
KEY user_name (user_name)
) TYPE=MyISAM;
Jan