I think it is the LCD (backlight being part of the LCD assembly). I had my share of that in my own laptop. One was resolved by reseating the RAM. On the other I had no choice but replace the whole LCD ( I am no good in backlight replacement
).
When I first encountered the same problem, I checked Google if there are other people experiencing the same. True enough there were others and the solution is to replace the LCD. example:
http://www.laptoprepair101.com/lapto...mment-page-16/
As for the cable you can do a visual check. The cable could be the culprit but very slim chance. You can only tell exactly if it is the cable or LCD, if you have extra parts to use like a spare cable or a spare LCD. Other than that, it would be impossible (at least for me).