Comment 8 for bug 728778

@wild_oscar:
> Also, this didn't happen some weeks ago,
> so it might have been introduced in a recent upgrade.

Might be as you say, but it might as well be because in the last week YouTube has been changing its player (to fix some issues), so maybe the new version of the player does something it didn't use to do, triggering a bug in the player that was already there but didn't use to surface.