http://blogs.msdn.com/b/david_sayed/archive/2010/01/08/firefox-information-for-hosting-video-on-azure.aspxThanks go to Tim Heuer for pointing this out (and providing this workaround). In the posts on hosting a Silverlight video player on Windows Azure, Firefox users will find that the embedded player looks like this when displayed in Firefox: Two things needen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)