This browser was able to play the videos, so Windows could not be the cause. Then I checked the situation with Slimjet portable.
My attempt, to show a blog post with an integrated YouTube video, the section with this video was blank. Your client has issued a malformed or illegal request. But during an attempt, to play a YouTube video, I received the following error page.
Then I interrupted my work and invoked Windows 7 power saving mode. I've created some blog posts during the day and I've opened a lot of YouTube pages, to check some videos.
