2008 Chevy HHR LT2 electrical problem

I had my New HHR LT2 for 2 days when it had an electrical problem. The gauges were all going up and down, messages flashing and svc lights all on. It was bucking down the road like the trannie was not shifting right. The dealer replaced the ECM and 2 days later ... same problem. I was traveling on the FL T/P about 75 mph when it started again. There was a post with a similar problem but it was a while ago. Anyone know the resolution?