Have the same problem, backlight comes on for a second when brightness (F1) is down and then press (F2). Earlier backlight would come on when moving screen up and down or closing it and oppening.
Have been told at Apple that LCD and inverter are OK. they did not mention any cables, but suggesten a new logic board £330.
Has anyone solved the problem cheaper? Should I get new Inverter cable (left side on logic board - very tiny) and "video" cable (right side on logic board - huge, complex cable).
Any advice appreciated.