Just had this same issue, black screen with mouse pointer showing, no desktop but ctlr+alt+del works.
I opened task manager and noticed that explorer.exe was taking only 6MB of ram when it usually takes 100+. Restarting it didn't work.
I then ran CMD.exe (click on new process) and it opened just fine. Tried to run SFC /scan now but it wouldn't let me because the user was not an admin.
Opened msedge.exe as a new task to try and find out how I can open a prompt as admin, and it opened just fine.
While I was doing that. The desktop showed up and everything seemed to work.
I was then able to open an admin prompt and run SFC /scan now, which said it found and repaired some corrupted files.
Currently finishing a virus scan and will see if it still works after a reboot, but hopefully this can be of use to others with the same problem.