LCD Backlight remains off after waking up, comes on at random.

My late 2008 Unibody MacBook LCD backlight has recently died. Note that the machine is out of warranty, and it uses LED backlighting - so no inverter. The actual display is still fine (just need a torch :P) and the external monitor output works fine (DVI). The backlight will sometimes randomly come on after a few hours' (sometimes days') use. Once it is on, it stays on and will function perfectly, but as soon as I put the computer to sleep or shut down, it will be off when I power up again. Restarting does nothing, the backlight is off throughout startup, so i think this is a hardware/firmware issue.

I'm not sure if it is related but prior to the issue arising there was a buzzing and an uneven backlighting pattern associated only with a low brightness setting. Interestingly, when the backlight does decide to work, this buzzing is no longer apparent at low brightness.

My guess is there is something wrong with the driver circuitry on the logic board, but I am confused as to why it should work fine when it wants to.