Have a Lowrance HDS5 that was working well today, but the screen froze. Powered it off, but now when you power it back on it brings up the Lowrance main screen with scrolling bar at bottom of screen, white tab scrolls across the screen one time then unit locks up and will not do anything else. None of the buttons will work. Unit will not power back off, only way to power it off is turning off main power switch on boats console.