rjsattler , TwasSnood , safeman
Didn't you tried "passive mode" rather than uninstalling avast ?
No I didn't try passive mode. I can try that on my other PC's running Avast that still aren't getting the update. And for those that have asked, I have not yet re-installed Avast on the computers I uninstalled the program from.
We know Microsoft is looking for antivirus programs before attempting to even download the patch. Many others have reported having an issue with other AV programs. I simply removed the roadblock as I saw it. We also know that Microsoft has made this patch a priority, therefore users should not expect to wait for the patch as if they are in a queue. If you are running Win10, the patch is available NOW. If you are running any version previous to Win10 (8.1, 8, 7), that patch will be coming on Patch Tuesday (Jan 9, 2018).
I will update this message after trying passive mode on the other PC's running Avast.
UPDATE: As suggested, I configured Avast for Passive Mode on the PC's with Avast still running on them. In both cases, the exact same result occurred: After the obligatory reboot to enable the changes to Avast, I went to Settings, then Update & Security, and clicked on the Check for Update button. Windows Update showed an update was available (it is the correct one) and downloaded the file. It then stated it was starting the installation and STOPPED before the update was complete. "Your device is up to date. Last checked: Today 7:10 PM". Further investigation shows that the patch was NOT installed.
In conclusion, Passive Mode does not resolve the problem, at least on my PC's. It appears that Microsoft sees that an antivirus is not actively monitoring the system and downloads the patch. But in the process of installing it, maybe it finds the presence of an AV program and fails so it doesn't potentially brick the system. This is just conjecture on my part based on research I've done on the problem today. YMMV.