Mine backlight is also always at 0% when I turn it on even though I set it to 100% before turning it off. Also, when external power is removed, the backlight goes to 0% - VERY ANNOYING AND INCONVENIENT!
I did a little more digging and found the following answer which works for me:
"One of the reasons for this setting is to conserve battery power if the device is powered up in a daylight situation. The original backlight setting is saved however and can be brought back up by simply pressing and releasing the Power button one time. This will bring the backlight up to the original preset level again. Another tap on the Power button will increase the level further."
