Hehe. Must have been one of those power supplies that are made to blow up at the beginning of the year. LOL
Nah, just kidding on that though.. One of the capacitors probably went out on you. The power supply I am assuming wasn't new and it sounds like more of a coincidence that it failed after being in your car. What I would do is test the output of your inverter for proper voltage WHILE the car is running. The inverter could have gone to **** on you and may be dumping out more juice than it is supposed to. Whether or not that is possible or if it would cause a problem I am not sure of, but it is at least a start.
Best rule of thumb with a carputer project, use all new stuff, dont dig around and use three year old dust collecting junk from your closet. There are too many new variables put into the equation when you start intalling a computer into a vehicle, it's best to know that it isn't the hardware that it causing the problem. Well, at least you minimize that possibility - also test your new hardware in the house on a standard power supply to make sure it works BEFORE you put it in the car.