Try viewing in another browser. Some of our customers have had problems with Internet Explorer and have been able to view in Firefox and/or Google Chrome.
Try installing the most recent version of Adobe Flash Player. That can be downloaded for free at http://get.adobe.com/flashplayer/.
One last thing to consider if you're still experiencing problems...
Pausing or stopping could be caused by a slow internet connection. Try clicking the play button on the video and then immediately click "pause" to allow the video time to download to your system. You'll see the progress bar expand as the video buffers into your system. Wait until the bar expands well beyond the player head and then you can resume watching the video.