What's wrong with my LCD Screen on JVC GR-DX67?

Hi, Can anyone help. Everytime I try to record a bright view using my JVC the LCD Screen flashes between a normal and a darker view. This flashing disappears when I turn the camera to a less bright subject. This flashing is also apparent when playing back the tape. This problem has only recently started. I did receive a "use cleaning cassette" alert but just on one occasion. Is it simply a dirty heads problem or something more sinister?
Regards
David