I just tried these videos on Chrome with my Macbook and they displayed properly. I noticed that in both cases, the video is prefaced with an advertisement. Do you have any ad blocking software / plugins running? If you right click on the area where the video should be, do you see the Flash Player context menu?
For videos other than youtube not playing...from any site. Go to GLOBAL SETTINGs in your Settings Manager
BE sure the tiny box marked 'Allow third party videos to play is checked' (it isnt' when you download originally!)
Then you need to allow your computer to download something by moving the 'Amount Stored lever right' to some amount. I would take a pic. But right now I cannot for the life of me figure out how to even get to my Settings Manager.