(digging up an old thread). The only thing I can think of is that the LCM flex is damaged or unplugged. The backlight is a separate connection, so if the LCM flex pops out or has been damaged (this happens quite easily) then you get a black backlit screen...

Disassembling the front panel is also a sure-fire way to break the flex too. I've no idea how they put them together in the first place!

Hugo