The map isn't the problem, so i wouldn't expect that moving it from Garmin folder to Map folder would alter anything. The problem is likely to be with the JCV file, however you have it in the right place (sd:Garmin/JCV/D2504090A) and if you've also tried another JCV file it's unlikely to be a corrupted file. Have you hard reset the Nuvi recently? If not, back up the files and NV memory and then hard reset it or better still also clear the Non Vol. but only after backup.