I was having the same problem loading version 2.1.7 of MediaElement as well. If you have access to ftp for your server, you can downgrade to 2.1.6 to fix the problem. Go here and click the “Downloads” button on the top right. Choose package 2.1.6 and save the file to your computer.
Upload the files you just downloaded to your wordpress install. I put them directly in:
/wp-content/plugins/media-element-html5-video-and-audio-player/mediaelement
Hope this works for you as well!