I can’t watch videos on Youtube.

I am having a problem here and I don’t how to fix it. My Windows is Vista, and I'm using Internet Explorer 7 for browsing. My JavaScript is enabled, Adobe Flash Player is updated, and yet why I can’t watch any videos on YouTube?
The message says, "Hello, you either have JavaScript turned off or an old version of Adobe's Flash Player".
Does anyone have a clue on this?
