This problem got worse before it got better. It got to the point that with some You Tube videos, I would get one play, and everything after that was white screen where the video displays. It was necessary to clear cookies, cache, etc., and restart to get out of it.
After a lot of research and testing, I found out that Adobe had made an upgrade, and they have a "hardware accelerator" that was causing the problem, and I needed to turn it off. You Tube actually identified the resolution for me. If anyone else has this problem, take a look at:
http://www.google.com/support/youtub...answer=1209379
Ralph Rayner