The problem you are experiencing might be related to low battery power. First, try replacing the battery.
If the problem persists, remove the battery, press and hold the Play/Pause button, and then connect it to the PC. Release the Play/Pause button when you see a pop up display. It will then try to install a new driver. This process can take up to five minutes. After five minutes, start the Device Manager software. This should rebuild the database of the player and can also take up to five minutes.