I bought a 73sv a year or so ago and bought the garmin ultra HD off Ebay for it and it works good so I bought a 93sv plus a couple weeks ago.i put the maps in the 93sv plus it said it didn't recognize it and would shut the maps down but it worked for a while then it stopped working,are they suppose to work on both?I have not registered the maps on garmin Express, would that matter?anybody got any ideas on it?