Flash
Update to the latest,
Restart the computer.
Sometimes, because there are too many cached files in the browser, your video can't be played normally. In this case, I suggest you turn off all your files first, then clean up the IE cached files, and then open them again to watch the video.
Of course, if you can't watch videos not only in YY, but also in other videos, then there may be something wrong with your graphics card. At this time, I suggest you repair your graphics card, otherwise other videos will not be visible.