Anyone having trouble staying logged in or logging in should check the date and time on their computer
Right-Click on the clock in the bottom right hand corner of your taskbar
Choose 'Adjust Date/Time'
Check to make sure your clock reads today's date with the correct time for your time zone.
XP when synchronized (third tab) with the outside time websites gives you an error if it is incorrect
Change the date and time to the correct one
THOSE WITH MORE THAN ONE PARTITION/OS CHECK ALL PARTITIONS AND OS's FOR THE CORRECT TIME AND DATE.