Two computer will not boot up!!!!

I have the same issue with two computers. One a Dell XPS and a HP.
Both instances the computers were turned off normally and when turned on the next day, The Screen saying the computer was turned off unexpectly and the options to start in "Safe Mode" to "Start windows normally" appear. Select "Start Windows nomally" and it will get past the Windows splash screen and the screen will go blank. Reboot and the same screen appears again and select "Safe Mode" and windows loads up 24 drivers and ends a "mup.sys". I did hardware diagnostics on both computers and everything is fine. Both computers have in common :
Window Media Center 2005, Norton Internet Security 2007, Webroot Spysweeper, the last windows updates and HP Printers. I did notice on the HP computer on the last shutdown that I received a "failed initialization" on some sort of HP Device.
Is anyone else experiencing the same symptoms. I do believe there is a software issue or major virus floating around.