Bewildering Boot Behavior

Folks,

I am asking for help with this behavior:

When booting into Windows 11, I see the Windows logo on screen, then the usual busy circle below it. Next, I would expect the credentials page to appear asking for a username and password. Instead, the screen goes blank, and the disk busy LED on the PC flickers, indicating heavy disk traffic. When I move the mouse, the cursor with the small busy circle appears for a short while, then the screen goes blank again.

This state remains indefinitely (I allowed it to run for about 10 hours).

Any ideas?

What I did to reach this state:
1. I created a new partition and installed Windows 11 onto it. It worked OK, and I could boot into it.
2. Then, I restored a Windows 11 partition from a backup into this new partition, replacing the newly installed Windows 11 partition, but leaving the newly created Windows 11 service partitions unchanged.
3. Using EasyBCD, I added an entry to boot into the new partition.

It does boot into the new partition, but ... see above.

Any help is appreciated!