I've NUVI3790T. I've copy Europe unlocked img but when GPS start show me that is impossible to unlock map. In hide SYSTEM folder there are gmapprom.img, gmap3d.img, gmapdem.img (but this is show on NUVI like unlocked), gmapbmap.img, gmaptz.img and other *.sum and gmapprom.gma.
I've generate gmapprom.unl but nothing, it is always locked.
I've also JCV folder and ASR folder with inside new files.
May someone help me?