I have a Explorist 210. A while back whenever I turned the unit on, it would give me a message about Configuring the NAND, no matter what I did it would just immediately shut off, when I would turn it on again same message same result. I don’t know exactly what NAND is but the factory, agreed to send me a Explorist 500 for free to replace it. OK deal says I! So the Explorist 210 sat on a shelf for awhile, until today I got bored and took the thing apart, 5 small Phillips head screws on the back. I separated the two halves and pulled out the circuit board, and then I pulled off the buttons membrane. I then hooked the unit up to my computer though the USB cord and turned it on. Got the same message, hit the enter button on the ‘joystick’ and something new happened! Instead of turning off, it said it was configuring! After a few seconds it did turn off. This time when I turned it back on, BINGO it’s working again!!! Stuck Button membrane was the cause of all my frustrations. But hey got a Explorist 500 out of the deal ;-) Hopes this helps anyone else who has had this problem.