Now this has happened to me in Firefox in the past and a quick Google search suggested I wasn't alone. It's ultimately a Flash/browser compatibility issue. A couple other Ad Age staffers have had the same problem; our web producer Charlie Moran suggested downgrading to Flash 188.8.131.52 -- that has worked for him.
But isn't it odd that it's happening in Chrome, Google's own browser? And it's strange that, as the world's largest video-sharing site, YouTube is having these issues. More to the point, how many views is it sacrificing when it fails to make it past the two-second mark?