Had issue with exactly the same problem come through the workshop this week and it turned out to be a bad seated connection on the back of the LCD...
Not something I would recommend as a test in any scenario really but try hitting the right hand side of the screen about halfway up (not with a hammer or blunt object of course), this might sound stupid but if by hitting it you see any flicker in video this might lead to it being a connection problem.
As I am typing this I have just repaired a macbook invetor cable (data) by soldering in a new fine cable on pin one which wasnt giving me a connection with my multimeter.
You gotta remember the invertor is resposible from changing a voltage from like 5V to like 70 thousand volts! Of course there is a very low current! But it's a big task I'm not surprised they conk out eventually especially considering where they live!