I have experienced similar problems with this program in the past and found that it would not work with some makes of SD Cards. Panasonic and SanDisk worked fine but several others could not be formatted with the Jukebox program, although they worked OK for Technics files in my KN7000. These were NOT of the 'el-cheapo' unbranded type of SD Card for example - Fuji, Kodak, Kingston and other make cards, just kept on throwing error messages..........
Could this be your problem???
Incidentally, I managed to use a 2GB card and it formatted OK but - it was a Panasonic card