Panasonic Viera TX-37LZD70F - Red 'CHK' message on... When I turned on my new TV everything seems

Question

When I turned on my new TV everything seems fine other than a red 'CHK' message on screen which I cannot get rid of. It is connected to to an aerial and a DVD player. The DVD is connected through a HDMI cable. The message appears on the creen when watching normal TV and DVD's. Presumably it means to check somethning, but what? Everything is connected fine. I cannot find anything in the manual about this message. Please help.