Holden Captiva 2006: Unexpected power loss

On several occasions all of the warning lights in our 2006 Holden Captiva LX have on come on with the resulting loss of power, which in turn makes the car go into ?limp home? mode. No one can seem to come up with a cause as the vehicle will run well for several days, then have a loss of power, then won?t start, and then be normal again. This is very scary.