Many functions, including most of the Music Box search functions are grayed out and not usable while you are driving. It can be very frustrating!
If you are confortable doing a little wiring, the thread at
zer...no-le shows (with pictures) how you can splice in a switch that prevents the speed signal from getting to the system, making it think it is stopped, and allow you to use all the functions of the Music Box, Navigation, etc that are normally grayed out while under way.
--jayhawk