Preferences error

Suddenly (I do not recall making any changes before the lat reboot) my "Guest" account is enabled. After one try to disable Guest login, I am no longer able to open Users & Groups preferences (I am the admin).

Has anyone encountered such odd behavior ? If yes, what is the fix ?

Thanks.

 

Solution found. For anyone having a similar issue, here is the solution:

Open "/System/Library/CoreServices/Directory Utility.app" and under "Directory Editor" remove "Guest User" and "Guest User 1" (apparently the "Guest User 1" is the result of some corrupted entry in the directory). Reboot and everything is back to normal: regained access to "Users & Groups" in Preferences and guest login disabled.