A few times after shutting down my Macbook completely, the fans have come on at high speed and the light stays on. The first time this happened, I allowed the fans to run for over an hour and they did not shut off until I pulled the battery. On the second occasion I attempted to boot the computer, but it would not boot until I held down the power button for ten seconds. The computer was not excessively hot, therefore I don't understand why the fans came on when it was shut down. The computer also seemed to get hotter as the fans ran rather than cooler. Any advice about a possible cause or solution would be appreciated. Thanks.