Well I've got a workaround to fix this, let me help you:
Let's do something quick, for example:
2) Right Click on the big video showing at the left, go to "Configuration" and then uncheck (deactivate) "Hardware acceleration"
3) Click "close" and Go to the video/videos where you're having trouble, refresh the page and the video should display correctly.
No matter if you clear your browser's data, all the videos from now will display correctly.
Let's wait for a Flash Player update in order to get hardware acceleration working properly...