The plugin does not seem to work with the new version of Download Monitor. I tried with the version that you have linked to on the main page, but apparently they have re-written the plugin, which is why the problem is occuring I think. I don't know if its happening to me only. The page didn't load completely when I used the shortcode : [email-download download_id="1" contact_form_id="2"]. Is it because the shortcode of the download monitor plugin has changed to [Download ID="1"] (Without an underscore) ?
Anyway, if someone's having the same problem, you can fix it by installing the older version of Download Monitor from here : http://downloads.wordpress.org/plugin/download-monitor.3.3.6.zip
It fixed mine. :)