I also had that problem last week, and nothing, and I do mean NOTHING helped getting it fixed. Permissions, Click2Flash, flash itself, Safari itself, cookies, cache, plug-ins, didn't have anything to do with it.
It was Google's HTML 5 Beta.
Surprise a Google Beta caused this problem, because, you know, Goggle calls every new product a Beta, even though the product itself is 3 years old (cough... Gmail.... cough).
Best solution is to leave the Beta for now and try again later. Hope this helps.😉