That happened to me once. I opened up my case and there were actually 1 inch tall gremlins in there gnawing on my cables and such. One of them must have pulled on the power button calbe or something. Anyways I called an exterminator and he told me he saw it all the time. In fact one time they pulled down an entire network in a major corperation. Well he fumigated my computer put up some gremlin traps around my office and havn't had a problem since