Invalid LiveUpdate Warning

I'm running NIS version 15.0.0.60 on Windows Vista home.  Whenver I reboot the computer, I get the following LiveUpdate warning:  "There is not enough disk space to install all available updates.  Click 'Yes' for help on freeing up disk space."  I have 74 GB of free disk space on my primary drive and 6 GB free on my recovery drive so this warning is invalid.  I've searched the symantec support area and this forum and can't find any reports of this issue.  Does anyone know how to clear this alert without reinstalling NIS?