The NAV was working fine, got home and took out the SD as usual and put it in the computer. I received an error from the TomTom app saying there is no SD card. Wonderful. This seems to be directed as a Mazda issue. Luckily, there is a solution, I hope: http://us.support.tomtom.com/app/answers/detail/a_id/16850/kw/backup to new sd card ...if this is a random and/or reoccuring issue it makes the NB1 even worse than it already is.