If you don't know it already, would it be maybe possible for you to disconnect your dvd player in your trunk in order to see whether you can still select nav screen and watch a vid? (from your previous posts I understand that you have nav + a/v installed in your car)
Read more: http://www.clublexus.com/forums/rx-1st-gen-1999-2003/706952-2001-rx-300-no-nav-cpu-video-input-nav-buttons-and-wiring-in-place.html#ixzz3tbeWw7bi