Go to: http://sarc.com/
Scroll down and click on,"Free Online Virus and Security Check" Write down exactly anything it finds, then return to: http://sarc.com/
and do a search for what was found. Symantec usually has a removal tool and/or directions for manually removing.
Found out there is a little trojan out there that sometimes creeps up and will do this, specifically changes the time zone but not the date. Maybe this is it, couldn't hurt.