I just thought I'd share this little trick I found to keep your screen from automatically shutting off when in the ACC position. Just access the Service Mode by press/holding down Menu, Map/Guide and Cancel (in that order). So now when you are parked with the engine off watching a DVD or playing a game your screen won't try to shut itself off.

But please NOTE: The automatic shutdown feature is there to prevent the screen from draining your battery. So I would not recommend leaving it like this for too long.

-nemogira