My ASUS MyPal A632 began to turn off by itself. It is not backlight, but the complete unit is turned off. Than very often it refuses to be turn on by switch on/off button. Only way to turn it on is to use reset button. But sometimes you have to repeat this few times until it stay stable for while. Then after while the same problem. Battery is OK! It is under warranty and I believe this maybe the case send it back for service?
Happened the same for me.
After lots of digging & googling I found the simple solution:
At the back of the PDA there is a "Hold" button. Change the position back and it starts to respond as usual before.
Usually answered in minutes!