I believe there is an incompatibility here. The below code does not work, yet if I remove the RadAjaxPanel, it works fine. Code below. Any suggestions would be appreciated since the entire site is RadAjax-enabled.
Unfortunately I have to confirm that this is an issue in this particular case when using RadAjaxPanel with hidden media player inside it. I will forward your report to our developers to address the bug for the upcoming version of RadControls for ASP.NET AJAX, expected at the beginning of the next month.
In the meantime consider replacing the RadAjaxPanel instance with regular MS UpdatePanel control. I tested the case locally and the media player operated normally under IE (it was not displayed under FireFox though).
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