'urlRoot' => '' did the trick. (I'm using XAMPP and my files go in the htdocs folder. so it was ending up looking in localhost/localhost/ directory).
Thanks for your help!
The 'localhost/' path is relative and was being appending to the root one, 'http://localhost'. That's why I suggested a path from the root (with a preceding slash), '/localhost/', or a complete path, 'http://localhost/'. But if it works for you with an empty path, keep it so.
Sorry, I don't know where might be the conflict between jQuery UI and the plugin you are using. You'll need to isolate the conflict code and analyse where the problem is. You have to dive into the code and do the trick by commenting single code lines that you think might be causing the conflict. Good luck!