Currently Being ModeratedFeb 1, 2013 2:21 PM (in response to grimsrudjk)
1. Install latest Adobe Flash Player.
2. Check whether you are currently in YouTube HTML 5 trial.
At the bottom left of the page uncheck the box for
"You are currently in the HTML5 trial".
3. Reset Safari.
Click Safari in the menu bar.
From the drop down select "Reset Safari".
Uncheck the boxes next to all items.
Check the box next to "Remove all website data".