This happened once to me 2 years ago on my 02 450ES.I had left the machine running for about 2 hours so I could use the lghts because I had put a moose down right before dark.I chalked it up to just getting a regulater or something too warm as it was fine after shutting it off for a second and restarting it and hasent done it since....Somebody here will chime in who knows im sure and i'll be interested as well.Good Luck.