With some of the recent updates to web browsers, we've had reports of videos 'stalling' when student attempt to view them. We've contacted Kaltura (company that hosts our video) and they report that it is an issue with the Flash player that is used to show smaller videos. The recommended fix for this is to choose the 'Large' video size when choosing a video to embed. This selection should not affect load time or quality, it just changes the size at which the video is initially displayed.
(Another workaround is for the student to maximize the stalled video, which changes the player to one that works.)