The most recent update of the Mac app seems to cause the video player to not work. DO NOT install this one. Is there any way to go back to the previous version?
The symptom is that the begining frame of the video is shown, but it will not start playing. The video can be downloaded and Quicktime will play it just fine. It will play on the web interface. The slider bar can be used to look at other frames, but that is ridiculously slow.