I just ran the update to 1.6.7. The Finder Window vanished; I didn’t get the usual prompt for my password.
I can see two processes TotalFInder and finish_installation, which does not seem to do anything.
An attempt to restart Finder using the “Force Quit” menu did not help.
Can I reboot my machine
After rebooting I tried to install 1.6.3 again; TotalFinder did not work.
I uninstalled TotalFinder and then re-installed 1.6.3; it came up immediately with the update to 1.6.7, this time it installed.