I'm probably not the only one with Safari 5.1.5 and Flash 220.127.116.11 who has Flash content go entirely black on pages like those on YouTube. In that case, if I really want to view the video, I quit and re-launch Safari, which makes the page come back with the video content displayed properly.
Given that this happens once or twice a day, I would live to find a solution better than the re-launch routine or to wait until either Apple or Adobe find the issue and fix it.
Does anyone have any ideas? I just looked at a thread that was started many months ago, where it looked like it had something to do with YouTube cookies and a re-launch didn't provide a work-around. This tells me that what I am experiencing is different.