i tried to unlock garmin topo Belgium 1725, after some tries i managed to unlock the map
i first used your line and added to gimgxore the *.imgfiles to a subdirectory (it did not work when i did it in the same directory)
for %f in (*.img) do gimgxor "%f" "newdir\%f"
then i copied the xored files back into the Original directory, afterwards i used unlockmapsource and it worked. (i did not get result with gimgunlock)
thanks for the help (please excuse my english)