Sounds as if you need to reflash the firmware. There a link in this post
to the version of the firmware that does a full reflash and format of the file system. Download it, unzip it, and put the resulting file in the root directory of your SD card. Reboot the Gen3 and, as soon as the first splash screen appears, press and hold the central button of the navigation control and keep it pressed in until the screen flashes white and the firmware updater starts. That should fix your problem.