Error retrieving a thumbnail from the URL

Hello there,
I’ve just installed the latest version of the plugin on my site http://www.musicaltv.al

However, something is not working properly as I am not able to retrieve thumbnails for any of the YouTube videos that I need.

My server has:
PHP Version 5.3.23
Wordpress Version: 3.6
It’s a dedicated server.

If I disable the pluging then the site seems to work fine (whereas when it is active the site does not work properly with the template).

Here is the debugging message I get:

Test Saving to Media Library

This test checks for issues with the process of saving a remote thumbnail to your local media library.

✖ Error retrieving a thumbnail from the URL http://img.youtube.com/vi/dMH0bHeiRNg/0.jpg using wp_remote_get()
If opening that URL in your web browser returns anything else than an error page, the problem may be related to your web server and might be something your host administrator can solve.
Details: name lookup timed out

http://wordpress.org/plugins/video-thumbnails/