I'd also suggest that you keep a digital camera in the car with you. The next time it happens, assuming you can get to a safe place to be stopped, take photographs showing the dash dark together with the lighted center display. That condition should never happen and being able to show it may give you some more leverage.
Better, yet, if you can, take a video of the dash and console and then you restarting the car, just to prove that you don't just have the dash brightness turned down.
Just FYI, that has not happened to me in 9 months and 11K miles of Leaf driving, nor have I heard of it happening to any one else. Small comfort, I know.
2011 Brilliant Silver Leaf SL
Reserved, quoted and ordered July 11, 2011
Delivered October 16, 2011 (Na. Plug-In Day)