We should contract out Caty [who does indeed rock] to Garmin support who want to charge AU$199 + shipping to supply a 'refurbished' exchange 3790 for this same problem experienced by out-of-warranty units. Seems a good system, their software breaks the unit and then they change you to fix it. Reminds me of a crooked glazier who used to slip a card under the door of local businesses and then the next night chuck a rock thru their front window.
In all fairness though, Garmin do give a 3 months warranty and it's also the same exchange charge even if your nuvi has been run over.