I've renamed the wp-content folder as descriped here.
wp-o-matic has a hardcoded plugin-path, so the installation fails because the JS-files aren't loaded correctly.
Because of the changed wp-content, this results in 404.
The exactly code is in wpomatic.php on line 73:
$this->pluginpath = get_option('siteurl') . '/wp-content/plugins/wp-o-matic';
Can you please change this? Sorry for my terrible english. :-(