- in hidden folder \.System\ delete the files gmapprom.img, gmapprom.unl and gmapprom.sum after backup on PC
- download new unlocked image version (normal NT for 1xxx, Unicode for 2xxx and 3xxx) and copy it after extraction (gmapsupp.img or gmapprom.img) to folder \.System\ - if it's named gmapsupp.img rename it to gmapprom.img (take care for exactly right name)
- replace *.jcv in ...