The bad thing is that our ASX support was a bit broken , and I had to fix it. This means that the currently released beta is not able to view the streams, you need to download brand new xpis from here: x86 / x64 (fair warning: these xpis are not tested at all, download at your own risk). Download, restart firefox and you should be able to watch the event live here.
(video is scaled 200%, quality is kinda bad, but that's how it's transmitted from NASA)
 IMHO ASX files are broken by themselves - they look like xml files but aren't (they don't escape special characters that xml files have to), and they're encoded in the current encoding of the machine generating the ASX file, and in order to correctly parse the file you have to know which encoding that is (the file itself doesn't know).