I have had a few problems lately with my blog : YouTube videos would not appear any more. I have tried to fix it in many ways (like embedding with javascript instead of HTML), but to no avail. Then I noticed that they would play correctly in Internet Explorer 7 (I am using Firefox 2.0). Filled with despair, I updated my Flash Player plugin from version 9.0.28.0 to version 9.0.45.0, and eureka !
You can check here what your current version is. So my advice is : stay up to date !
Labels: Flash