This started on one site using version 2.9.1 of the plugin and 3.4.2 version of WordPress, along with the Sermon Browser plugin. I was using another audio player, and switched to medialelementsjs for viewers using iPhones and iPads.
Feedback from those users is great. However, in IE, the sermon will stop at 4 seconds and not continue (it doesn't seem to be a buffering issue, it simply stops.) Also, the timer on the right side (total time of the mp3) reads NaN:NaN rather than the actual time of the file. It works perfectly fine in Chrome, Firefox, and the mobile browsers. Tested on several laptops, desktops... behavior is consistent.
I am currently building another site, and using the mediaelementsjs plugin and shortcode. I upgraded to WP 3.5.1, and began using the 2.10 version of the plugin. Not only did the same issue persist (player halting at 4 seconds in IE only), but the play/pause button and the speaker icon were missing from the player. Functionality was there, but no visual clue. I "downgraded" to v. 2.9.1, and the buttons were back but the halting playback remained.
The two sites:
http://rockvillebible.org/sermons/sunday-morning (using mediaelementsjs in conjunction with Sermon Browser plug in), currently WP 3.4.2 and mejs v. 2.9.1
http://vbc.larennetworks.net/sunday-message/ (using mejs v. 2.9.1 via shortcode, WP 3.5.1 Multi-site testing server install)
Any suggestions, further questions, similar situations.... would be appreciated.