Acrobat XI Pro - update failed - no error code

I have Acrobat XI Pro installed in a Win 7/64 environment.  It presently reports being at version 11.0.16 under HELP-About Adobe Acrobat XI Pro ...

When it checks for updates automatically, it finds one available and throws the icon in the tray at the lower right.  Alternatively, when I go to manually launch the updater, it brings up the Adobe Acrobat Updater window indicating that "Update is Available".  When I select DOWNLOAD, it throws the icon in the tray at the bottom right of the screen.

In either case, when I click the updater icon in the notification tray, it brings up a window indicating that "Update is ready to install".  Selecting INSTALL results in the Windows UAC window asking for the administrator privileges, and then reports "update failed" immediately, with no error code.  This is very annoying.

For the time being, I have disabled automatic updates in the EDIT-PREFERENCES-UPDATER window, but I am wondering what the heck is going on and why such a cryptic message from the Adobe Updater.  Any assistance would be appreciated.

---tbg