Unity 5.4.2f2 will not launch in Windows 10 (Windows update over weekend)

Unity 5.3 has been running fine on my system for months. No hardware changes.
Over the weekend, Windows 10 updated itself.
This morning Unity 5.3 would not run. It launches, nothing at all appears on screen – no project load screen, no license or login screen, nothing. Task Manager showed Unity.exe running using 0% CPU.
Tried all of the “fixes” I could find here, including running from command line forcing it to use OpenGL modes, specified a log file location – no changes, same result, and never creates a log file.

So I completely un-installed Unity, and installed the latest version (5.4.2f2).
Exact same issue. Unity.exe shows up in task manager using 0% CPU (and some memory), but nothing visible ever happens. Same tries with command line options.

I’m completely at a loss. Help?

Did anybody solved the problem?
Would be very nice for any hint :slight_smile:

Thanx, Matthias