Problems turning my Vr-500 on

When I turn my VR-500 on the screen goes through the usual display 
scrolling YAESU VR-500 and then the screen goes blank and a small 
highlighted blinking "5" or "S" appears at the top right of the 
screen.  Nothing can be done after that. Sometimes the blinking stops. 
The only thing you can do with the VR-500 is turn it off.