Are you using the JCV file that came with the 2012.20 map with the 2012.40? If so, dl the compatible one from this thread and place it in a "JCV" sub-folder of unit's .system folder, with the 2012.40 map image in a folder named "Map" in the root. You can use any convenient name in the Map folder eg "CN_NT_SAf_2012.40.img". If either folders doesn't exist then create it. Paths are like this:
x:/.system/JCV/xxxxxx.jcv
x:/Map/xxxxxx.img
You can also place them in the micro-sd, which is really the best place for 'unoffical' maps in case something goes wrong. Just remove the sd and problem fixed. Paths in sd:
x:/Garmin/JCV/xxxxxx.jcv
x:/Map/xxxxxx.img OR x:/Garmin/gmapsupp.img (only gmapsupp.img will work in sd's Garmin folder).

Forget about 3D, ASR and G2S for your unit. They are for 3D display, speech recognition and traffic which are not used by Nuvi 40. See [Only registered and activated users can see links. ]. Info on your unit spec's:
Code:
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Maybe have a browse thru here as well: [Only registered and activated users can see links. ] to bone up.