j'ai un erreur à la désactivation de certain plugins notament GThumb+

[mysql error 1062] Duplicate entry 'GThumb' for key 'PRIMARY'

INSERT INTO piwigo_config (param,value,comment)
VALUES ("GThumb" , "a:7:{s:6:\"height\";i:200;s:6:\"margin\";i:10;s:13:\"nb_image_page\";i:80;s:9:\"big_thumb\";b:1;s:15:\"cache_big_thumb\";b:1;s:6:\"method\";s:4:\"crop\";s:22:\"show_thumbnail_caption\";b:1;}" , "GThumb plugin parameters");

#1    my_error C:\wamp\www\piwigo26\include\dblayer\functions_mysqli.inc.php(109)
#2    pwg_query C:\wamp\www\piwigo26\plugins\GThumb\maintain.inc.php(12)
#3    plugin_install C:\wamp\www\piwigo26\admin\include\plugins.class.php(48)
#4    DummyPlugin_maintain::deactivate C:\wamp\www\piwigo26\admin\include\plugins.class.php(191)
#5    plugins::perform_action C:\wamp\www\piwigo26\admin\plugins_installed.php(73)
#6    include C:\wamp\www\piwigo26\admin\plugins.php(46)
#7    include C:\wamp\www\piwigo26\admin.php(293)