Why does the NHL blackout notice come back onscreen after changing channels?

Obviously, Comcast will not allow DirecTV customers to watch any Philadelphia Flyers games, even away games, on another city's tv channels, or even the NHL Network . But why does the blackout notice block my screen after changing channels, and even power cycling the DVR and TV? I'm watching NCIS on TNT, and the screen is blocked by the Game Search error notice.