I recently purchased a Professional 520, the unit charged up and I managed to add my phone etc. when I put it in the truck and connected to the USB it failed to charge. I took it home and put it back on charge for at least two hours but it failed to reboot. I then took it back to the shop where it was purchased and was supplied with a replacement. Guess what: Exactly the same thing has happened. What am i DOING WRONG?