Does anyone have the same issue?
When I open Settings and click on Sharing, I get the Authentication required dialogue (The password you use to log in to your computer no longer matches that of your login keyring.):
My user’s password is not accepted.
I guess that this could be related to one of the passwords in the Sharing menu.
Note that I didn’t even enable any sharing option.
seahorse in terminal and see if you can find the keyring password.
Did you change your user’s login password?
Oh, yes, I remember that the password set during installation was suddenly not working anymore. So I was using Rescue Mode to reset my user’s password.
(Later it turned out that this was an issue with my shift key not working reliably :-/)
But this was about two/three months ago.
UPDATE: today, I wanted to continue troubleshooting, but now I cannot make this dialogue appear anymore.