How do you resolve the javascript error in Youtube videos?

I have had this problem for a while but finally decided to stop being lazy, take a screenshot and find out what’s going on. On certain youtube videos, I cannot see the video because it says my javascript is turned off or i am using an old version of Adobe flash player. So I usually have to download the video and watch it via VLC. But the SAME video works for me if I watch it from the uploader’s profile page and this problem is not with some specific uploader’s. For example, if a user uploaded 2 videos, one might work for me and the other won’t. The screenshot example was taken from this video . As the screenshot shows, it tells me to download a new flash player, which I have down countless times to no avail. I think it has to do with javascript but I also think my javascript is turned on (though I am not sure, how do i figure that out?). I use Windows XP, and the problem is in any browser (FF, IE). How do I fix this?