"User already logged in" when trying to join Microsoft webcast in IE

Hi. I'm not sure if this is the right place for this question, as it has to do with a Microsoft webcast that's coming up in about 20 minutes.

1. I follow this link: https://vts.inxpo.com/Launch/Event.htm?ShowKey=20809
2. Log into the site.
3. Get error in red saying: User already logged in!

I wait a few minutes and try again; even try other browsers, clear my cache, and still get the message. Help! Why would it not let me join a Microsoft webcast?