I have met my match "file name is not valid" and "no more files"

I'm generally pretty self sufficient on Windows, and have gone 9 years on the same laptop (an Asus M50VM-A1) without issue. Until now.

I am receiving "the file name is not valid" and/or "there are no more files" errors any time I try to Save As any document type from any program: a TXT from Notepad, a PNG from Edge, a PDF from Chrome. You name it. So I cannot save any new files. However, resaving old files still works.

Here's what has me stumped:
-Full scans of Malwarebytes and Norton 360 (with all updates) show no issues.
-Windows is fully updated.
-SFC /scannow always shows that "there are some files that could not be repaired", even when run in all 3 safe modes. However my laptop has ALWAYS reported this with SFC, with no issues till now.
-A full system restore to a date before I was still able to Save As, had no effect.
-Neither did disabling internet connectivity, defragmenting, cleaning the C: drive, etc. Of course, I didn't expect them to.
-In the safe modes, I am able to Save As. I cannot in normal mode, or with a clean boot. This seems to indicate to me an MS problem.
-Shutting off Norton's antivirus and firewall has no effect. Neither does Norton Autofix, stopping the Asus Security Data Manager (ASDM) service, or moving the ASDM program folder so it cannot be executed. (Other forums suggested this program could be the culprit.)
-I've even tried going through Task Manager and shutting down as many programs and services as possible. No effect.
-I have no other security software other than the aforementioned, and have not installed anything new recently. However, C++ Runtime 2015 shows a recent installation.

The only possible culprits I can think of:
(1) I ran CCleaner's registry cleaner recently. But I have done that for years and have never had a problem before, and none of the keys it removed appeared to be Windows-related.
(2) I think this started happening right after MS released the major security updates across all recent platforms, even XP. But wouldn't the System Restore have rolled those back?

Help? - and thanks in advance.

Hi, please see:
Save as .....There are no more files - Windows 10 Forums

Asus related- you have an ASUS laptop.

9 years- wow. My Asus lasted 2.5, and I had a MBO failure in warranty, and the same symptom when it died.

SFC /scannow always shows that "there are some files that could not be repaired"

In build 1511 (November update) there was a long-standing bug where an Nvidia file Opencl.dll was always flagged. But hopefully your build is more recent than that. You can gain more by examining the CBS.LOG of course.

I had the slight advantage I recalled having seen the problem listed briefly- I just searched by "there are no more files". But you just can't always rely on searching with exactly matching text. (My current laptop - by a good company- does happen to have an ASUS MBO I discovered...but unusually these days most of the back comes off, + good ventilation, and 3 year warranty).

If you read that thread through it goes on to uninstalling the thing.

See e.g. #20.

Revo Uninstaller Portable Download

Here's a portable version- no installation. Never tried the portable version myself..

But reading your post again after your comment suggests you have more and deeper issues. Anyway, start by trying to uninstall that program.

What is your Windows version?
Windows key + R, winver