Norton Internet Security 2013 computer stuck on boot screen

Hi,

I have NIS 2013, and recently it detected a virus on a pen drive and deleted it, and requested that I restart my computer.

 

When I restarted the PC, it goes to the boot screen and displays a message

"Symantec is is cleaning threats from the computer and will restart when completed. Don't turn off the computer..."

..and it stays on that untill I force re-started the PC. I even waited for over four hours.