Short in the machine or power surges from the power company would be my first thoughts, followed by a bad circuit board. Do you have problems with other electronics in the house? Light bulbs that seem to burn out prematurely? If so, talk to the power company and ask them to test the peak voltages supplied to your house. In an area with rapid growth and not quite enough power lines, it's not uncommon for the company to turn up the voltage a bit.

If there's no signs of overvoltage supplied by the power company, take the machine in for service -- it probably has a short or bad board.