Warped Factor,
Glad to hear you scared your computer into behaving itself again.
I was thinking about possible causes. One thing that is known to affect the clock is Antivirus programs, another is actual viruses. (Just thinking that you set the clock when you start the computer, but do not notice the time on the screen when you shut down. No one looks at it on shutdown.) It could be the time slows down while operating the computer and then when you shut down it is already off by an hour or so.
If you just want to do a scan of your computer to check for Viruses, run:
Trend Micro's Housecall
The power button the front of your computer should be a push button which is a "Soft Off" and the rocker switch on the back of your power supply is the actual power shutoff for the computer.
Take Care,
Richard
P.S. Looks forward to seeing you in January.