Screen looks like it has

Screen looks like it has a black criss-cross type film over the picture - varies from one place to the other. TV is on cable and cable is working because other tvs in house are working fine. We have "Moxi-box" with the cable TV and was working fine when we turned it off, then had the black on it when we turned it on again. We still can see all programs and the cable "box" does all it's functions, but just have a black "film" over the picture. Can you help?