I don't see any ClickToFlash markers YouTube videos play just fine, and AdBlock is apparently not involved.
If by "ClickToFlash markers" you mean the gray rectangle with the gear icon in the upper left corner and the Flash button in the middle, I don't know why you're not seeing it; that's what I see, although the button reads "YouTube" at first, and only switches to "Flash" once my cursor moves inside the gray rectangle.
When the button is clicked, the movie loads as expected.
(As for AdBlock, I do have the
Block ads inside YouTube videos option checked, but got an ad nevertheless...for cat scans.
)