This is odd. Around 1:30am pst (Feb 23 ’09), movies on youtube have stopped working. As if there was a glitch that has all flash flv being selected instead of the h.264 codec coming up. I did a quick check on twitter and seems others are having the same issue. The odd thing is I can sometimes get it work when in edge only. … scratch that, now edge is not working either… Hmmm..
I found a workaround..
Go to www.youtube.com and play your videos from the website. Not every video will work because the search results provides videos whether they are flv or h264. This is clearly a work around (hack) till they get this fixed, but at least you can get your youtube fix.