I would try re-seating the cable for the backlight, and also the backlight itself may need to be replaced. I don't know if they have replacement bulbs available for the iBooks or not. Last time I was changing them out was on some old POS systems that were running Windows 98. But, I would try the cable first as it will probably cost next to nothing, then move to the backlight if you're still without success and then, if still no progress, I would probably just try a new display all together. The issue is definitely with the display itself. You can narrow it down to the display cabled, or the backlight inverter board, or the backlight itself. Honestly I would probably lean toward the inverter board if it's flickering on and off again. Either loose connection or a bad board.