Sorry I have no idea why the box should work then sudenly stops working, have never heard it do that before. When you state stops working what do you mean, how long does it work ok, does the screen freeze or does V6 disappear from the screen or do flights just stop showing, can you describe more than stops working?
Do you have Get Flights from the Airnav Network flights ticked on the network tab, if so untick them
Alan