2000 Dodge Intrepid problems

My son has a 2000 Dodge Intrepid. In June '11, the dashboard started acting up. When the car was started the dials would work for a couple of seconds and then the dials would stay at 0. Finally, the battery died in Feb. '12. Battery was replaced and alternator was checked out as working properly. Car died a couple days later & we couldn't get it checked until July. Determined the new battery was defective. Alternator was checked again and was working fine. Battery replaced. Car worked fine, including all the dashboard gauges & speedometer. A few weeks later, the dashboard started acting up. A few weeks after that the car won't start anymore like the battery was dead. Any suggestions about what could be wrong?