How can I fix it - TOMTOM GO 510?

I have a tomtom GO 510 and was attempting to add the TOMTOM Home to my computer and see if there were any updates. The programme downloaded to my computer but when I tried to import any information to the sat nav there was an icon in the bottom right stating that the device was not connected. I checked all connections and they were OK, but still nothing. When I closed down the computer the sat nav would not turn off, the screen was eluminated all the time, but nothing on the screen. The on/off button made no difference. After about 8 hours the screen went off. I have put the sat nav back into the docking station and the on light came on again, but there is nothing on screen not even any elumination