well, ur supposed to copy the GMAPSUPP.IMG to top level directory inside /Garmin folder of the memory card, where ur SW.UNL is.
ur /garmin folder 'should' contain the following ONLY -
Apps,Cache,EULA,Font,GPX,Images,JPEG,POI,vehicle,Voice for folders and
GarminDevice.XML, GMAPSUPP.IMG,SW.UNL...