I have had the same problems with no power. I also took it back to the dealer three times, with the same results as the previous post. 1st time they told me it was a loose battery cable, the 2nd and 3rd time they said that the battery voltage was reading too high and if it reads too high or low, the car stops.
Now there is a new problem with it.
While I was driving it today, the radio went off, the seat belt light came on, and the car started to stall. This happened 3-4 times in a 2 mile stretch.
The gas mileage is good - assuming the car actually moves.
Dude I think it's your alternator... something is wrong with it for sure...