I got a popup to install an update to the Update Manager. I first clicked on information to check it out on the webpage. Then I clicked on the button to start the upgrade. I immediately got a msg. that the file can't install, that it might be corrupted.

Open Nexus Ultimate Preferences, go to the Advanced tab and click the Check for Updates button.

Does the same thing happen again?

Yes. Same error message.

Thanks. I installed Nexus Ultimate v15.9 on a clean test system here in case the problem was a bug in the Update Manager itself, but nope. It notified me of the update and correctly downloaded and installed it.

Which leads me to believe the problem might be on your system.

Can you please post a screenshot here of the contents of two folders? They are:

C:\Program Files (x86)\Winstep\

and the other is

C:\Users\Public\Documents\WinStep\Versions\

Here's the program folder. The version folder is empty. On my computer, the folder is C:\Users\Public\Public Documents\Winstep\Versions.

Damn. One of the things I wanted to see was the folder structure inside

C:\Program Files (x86)\Winstep\

and that is unfortunately not visible in your screenshot.

Also, can you drag & drop a file (any file will do) into the

C:\Users\Public\Public Documents\Winstep\Versions

folder without having a UAC prompt requesting permission?

Could you be more specific of "the folder structure"? The only folder inside the Winstep program folder is "Help."

Yes, I can drag/drop a file into the other folder without any messages.

I'm running the full Winstep Monty, not just Nexus, but the update installed fine, here.

It installed today.

Eh? lol

Don't you just love this self-correcting 'bugs'?

I actually fiddled with the Windows Update Manager code last night and already had a 'test' version for you to install to see if that solved the problem.

Then I wake up and immediately get into emergency mode due to the problem with the faulty Microsoft Windows Update patch (before I knew the patch was to blame, of course).