Outlook suddenly unloads Norton anti-spam add-in

I have been running NIS 2010 for almost a year and the anti-spam function worked perfectly within Outlook 2007 until this past Monday (November 1).  Outlook suddenly disabled the anti-spam add-in and all configuration or setup changes that I tried made no difference.  The add-in was listed as "unloaded".  So I finally completely uninstalled and then re-installed NIS 2010, and things looked fine for about 24 hours.  Now I am back without my Norton anti-spam filtering and toolbar.  What is wrong?  I made no changes that I know of to make this happen.  Note that incoming spam messages ARE labeled [Norton Anti-Spam], but they are not moved to the Norton anti-spam folder -- and the Norton toolbar is missing.