Does the bike just make a clicking sound from under the seat and the dash re-sets?
If so, the most likely cause is a drained or dead battery. These big twins need all the battery juice they can get to start. If the battery falls below a certain voltage (something like 11 volts), the dash will re-set itself. If your bike sits regularly for more than 2 weeks unused, then a automatic battery trickle charger is recommended.
Other possible causes, have been...
loose ECU main connections
loose wires to the battery
fouled spark plugs
If you do get a new battery, follow the instructions on the initial charge exactly. This has the biggest effect of long battery life. Yes, batteries can go dead in as little as 1-2 years, if not properly maintained, or initially setup.
Click below for info on re-setting the Mille or Falco dash back to original settings.