Try rebooting the computer, I had the SatNav crash on my Camry and ended with a black screen. Easiest way is take the fuse out, I can't remember which one it was unfortunately, I just took each one out of the box under the bonnet in sequence (leaving a few obvious ones alone) until the whole Nav/Audio/Screen etc didnt respond, put the fuse back in, screen lit up saying please wait for a minute or so then it was fine.