Selecting/Deselecting Maps

 

I've been experimenting with loading maps from GPS file depot onto my Nuvi 200 either into the unit or on an SD card with good results. Yesterday however, it wouldn't let me select City Navigator until I did a major reset on the unit. Now I can use City Navigator again, but I can't deselect it if I wanted to switch to a topo map or something else covering the same area as the Garmin map. Transparent trail maps will work with in conjunction with City Navigator, but I'm wondering how I lost the ability to select/deselect it.