Activating Crypto Captcha generates:

[mysql error 1062] Duplicate entry 'cryptographp' for key 'PRIMARY'
INSERT INTO piwigo_config (param,value,comment) VALUES ("cryptographp",'a:15:{s:15:"comments_action";s:6:"reject";s:5:"theme";s:4:"gray";s:12:"captcha_type";s:6:"string";s:14:"case_sensitive";s:5:"false";s:11:"code_length";i:6;s:5:"width";i:120;s:6:"height";i:40;s:12:"perturbation";i:1;s:14:"image_bg_color";s:6:"ffffff";s:10:"text_color";s:6:"8a8a8a";s:9:"num_lines";i:2;s:10:"line_color";s:6:"8a8a8a";s:11:"noise_level";d:0.1000000000000000055511151231257827021181583404541015625;s:11:"noise_color";s:6:"8a8a8a";s:8:"ttf_file";s:9:"TopSecret";}',"CryptograPHP config");

#1    my_error C:\wamp\www\piwigo\include\dblayer\functions_mysql.inc.php(88)
#2    pwg_query C:\wamp\www\piwigo\plugins\CryptograPHP\maintain.inc.php(41)
#3    plugin_activate C:\wamp\www\piwigo\admin\include\plugins.class.php(101)
#4    plugins::perform_action C:\wamp\www\piwigo\admin\plugins_installed.php(73)
#5    include C:\wamp\www\piwigo\admin\plugins.php(48)
#6    include C:\wamp\www\piwigo\admin.php(273)