2007 Pontiac G6 Fuse Box short?

My car gave me a message: "engine power reduced" and then stalled. The third time it did that within 12 minutes (in the middle of morning traffic) I had it towed to my dealership where I was told that it was a short in the fuse box. When they quoted me a price of over $600 I questioned why a two year old car would have a short in the fuse box (not the fuses that had the short). I was advised that it's a defect in the part and they did not know why it shorted out. What is the fuse box? Why would it short out all of a sudden? And if it was a defect in the part, shouldn't the dealership or the factory replace that free of charge to the consumer?