Can't Listen to Any Lessons on My Mac

Hello -
I’m trying to listen to the lessons on my Mac but the player just says 0:00 - ?:?? and nothing plays when I hit the play button. Is this a common problem? I also cannot launch vocabulary cards.
Thanks!

Would you be able to let us know which browser you are using? Also, make sure you have the most recent version of Flash by going here: http://get.adobe.com/flashplayer/