Electrical Failure problems of the 2007 Hyundai Accent

I own my new car(Hyundai brio 2007) since July,14,2006. For over six times it have present the same failure; it turn off the engine while riding ,then suddenly stop and don't' turn on again. I took it to the dealer by towing several times. The repairs took some weeks each time,they replace three batteries in past three years,fusible or board,they said is was electrical failure of fuse, but failure were not solve. Last Sunday,may,9,2010,it happens again. And this time me and my family were very nervous,because the car turn off while riding on the highway at 55 to 65 m. P. H. And suddenly stop on the road. I call for towing and took the car to the dealer. It has pass five days and nobody knows how to solve the problem. There's no diagnosis . I'm really afraid to use this car again ,because my family life is on risk.