Format the file system (see below). If and only if the menu is not accessible, then attempt to restart the controller multiple times until successful.
Format File System Process -- most updated firmware version (1.8.1.0.); this may change in future.
Menu>SystemSetup>6. Advanced> More>Button 3 for Clear Data>Format File System (button 2)
Note: This will NOT erase all memory settings in which they would have to be reprogrammed.