This is a known issue with Chrome users. Chrome comes with built in plugins--One of them is Flash. They have been slowly disabling the Flash plugin on the browser for some users in waves. This is why the problem is sporadic. 

I use Easy Video Suite to play the videos for you. EVS uses Flash as part of the player code. The solution is for EVS to update their player code so that it supports HTML 5. I'm told that the fine folks at EVS will be making this update in the near future.
 EVS has put out a video explaining one way to fix the issue: Watch this short Video

This should fix the problem for you. In the alternative, you may also switch to Firefox, which does not seem to be affected by this issue.