Why did Windows Server restrict the rights of all users, including "Administrator"?

Question

Windows

The trouble came suddenly.
After the next reboot of the server (it would be more correct to shut it down abruptly), all users lost their rights to access files in the system, they work mainly remotely via RDP. To exclude questions about the system on which the server is running, this is Windows Server 2008 R2 Enterprise SP1 x64.
What I tried
- I tried the crutch method - assigning a new owner to critically needed files and folders, did it manually.
- I checked the presence of the included "Administrator", it is included.
- I delved into local policies, but due to my ignorance of the issue, I did not dig up anything useful.
Assumptions
- The system has driven itself into some special security mode, then a reasonable question arises how to get it out of it.
- The "Administrator" has flown, but the account is there and it is enabled. It is not clear why he fell out of the owners of the system (forgive me if I call it something wrong).
- I haven’t installed updates for a long time, it may well be that due to the lack of updates, the system became alert, but since I can’t stop the server (reboot and shutdown) yet, and this will be needed to apply the updates. This option was left for the last resort.
If anyone has any suggestions on how to solve the problem, I will be very glad to hear it.

Answer 1

Can you roll back to the last checkpoint? If they are, of course...

Answer 2

In my opinion, there is no such thing in the server platform ...
but can you describe the problem more precisely? log screenshots?

Answer 3

Contact the administrator, to be honest, after a hard reset, anything can happen to the data on the disk.

Answer 4

Did you check for file system errors? bad test? maybe some files were screwed up...
and I don't understand the manual setting of the owner, and the subsequent assignment of NTFS rights, which did not help?
Boot from the live CD and see how it goes...