You can watch the video clips one day, and then you cannot next day (or vice versa)... This issue seems to be known since late January (a lot of people have complained/reported the same problem), and the staff of Blogger.com are trying to solve the problem now.
It seems it doesn't matter which computer or browser system you are using to watch these videos. For example, I could watch these videos on my Mac computer about 3 times out of 6 times, trying at different time and day, and I used two different browsers (Firefox and Safari), but it didn't make any difference.
So, the chances are, even if you couldn't watch the video yesterday, you may be able to today. So if you don't mind trying again, please do so.
I am sorry for the inconvenience and frustration this problem may cause... I hope that the Blogger staff will solve the problem as soon as possible!