The solution that worked for me was found in this thread:
No need to uninstall/reinstall, just set Full Control permissions for the Users group on the registry key:
HKLM\SOFTWARE\Microsoft\Office\ClickToRun\REGISTRY\MACHINE\Software\Microsoft\SecurityManager
Open Regedit (Make sure you are admin) Go to the path above in the reigstry. Right-Click on “SecurityManager” and select “Permissions“ In the permissions window, look for the “Users” group and make sure Users have “Write” access. Click the Apply to make sure the settings take.