I found the file class.plugin-modules.php in the plugin that I downloaded, wp-vcd.php file comes from this file, for you who like to download nulled plugin or themes my suggestions before doing the installation try check first whether there is this file or not. I hope this helps
I think update_option is part of the function of this plugin, it turns out that the default function wordpress :P, the problem is solved with a little modify ajax, thanks plugin is very cool.
