What format do you format the SD card with - fat32? Or just delete it?
Before this, I just updated this folder maps \ 00 \ nds \ PRODUCT and my navi could not start anymore, I put the correct card in, again and after a few restarts, it worked again with the original card.
And.
I have a newer version, (Replaced /maps/EEC/EEC_WLD/OVERALL.NDS on the SD CARD with that from my original backup of 0430), I just have to take the file from my 0730 instead of 0430