Sounds to me like you need to have your hard drive looked at! It's amazing how these things occur when you have just done something which leads you to think the computer has been affected: on December 31, 1999, amid all the hullabaloo about the Millenium Bug, my laptop was set to Moscow time, but I was in the UK (3 hours time difference). Finishing off something or other on the laptop before the big New Year party, I was dismayed when the laptop shut itself down promptly at 9.00 p.m. UK time (i.e. the stroke of midnight on the computer clock!). The Millenium Bug had struck! Or so I thought! No amount of coaxing would persuade the thing to come back on! When I finally got it to a computer specialist a couple of days later(yes, January 2), it turned out my hard drive had simply chosen that precise moment to crash, no bugs, no nothing, just sheer exhaustion from years of overwork! Luckily, we did manage to retrieve my most important data files, but that was a lesson for me in always making a backup, I can tell you!