NIS Suddenly Downloading Large Data Even When Fully Updated

(Still!)Running WinXP SP3 with Norton Internet Security (NIS) version 21.7.0.11.  NIS is set to run Auto Live updates and Pulse updates. Using Networx Data Monitor tool to watch my real time data usage. Two days ago started noticing very large data download starting. Exited Firefox and email and large download still continued. Killed internet connection and rebooted and when back online and after a minute noticed large download starting again. Killed internet went to every app I had to see if auto download or its equivalent had been turned on and found nothing that might be doing massive update. Became concerned and ran a full system virus scan, ran Malwarebytes and Malwarebytes Anti-Rootkit tool - all came back clean. Found and downloaded NetLimiter 3 so I could see what was using my bandwidth and how much while I was online. Low and behold, the culprit was NIS. After couple minutes and 75MB it looked as if NIS was downloading the full definition file! Killed internet and went to church to use their system and downloaded latest definition file (about 450MB). Came home and ran the .exe and it updated NIS, which showed a big green checkmark and that it had last updated 37 seconds ago-Great! Went back on line and things seemed fine. This morning fired up and saw large download occuring and once again NIS is culprit. Has anyone run into this before? Do I need to uninstall/reinstall NIS and update with latest def file? Thanks!  Gene