NIS Crashes Vista During Idle Time Scan

I have been running Norton Internet Security for almost a year now without any problems until now.  Whenever Norton’s does an idle time scan, it locks up the computer requiring powering off and rebooting.  The computer is a Dell Inspiron 1520 running Vista Home Premium.  I don’t even know where to start to solve this problem.  Any help would be appreciated.  Doing a search didn’t help me either in this forum or on the Internet at large.

 

Chuck