My 19 inch Panasonic Freeview HD-integrated TV has developed an annoying habit in recent weeks where it flashes black a couple of seconds after changing channels. This usually only happens on the HD channels. Granted, it's only a minor irritant, but I'm worried it could be a worrying sign. The TV's out of warranty, but, as I bought it from John Lewis, I got a 5-year-guarantee with it.

So is it over five years old?, if not it's still under warranty, just JL's.