Can't update Norton Utilities

I keep getting the message "Core product files have been modified Please run Smart update or reinstall the product."  on Norton Utilities version 16.0.2.39.  I run smart update which downloads and installs 5.42MB and then tells me to reboot, which I do.  After reboot the version is still 16.0.2.39 and I get the "Core product files have been modified Please run Smart update or reinstall the product." message again....  I have even tried re-installing NU from the website, but that just downloads 16.0.2.39 again - how do I get version 16.0.2.53 installed?