Violation of UNIQUE KEY constraint error when verifying a user in Content Studio

When an administrator tries to verify a user registered in Content Studio the error -2147217873 "Violation of UNIQUE KEY constraint 'Cstr_Users_DomainUsers'. Cannot insert duplicate key in object 'tbl_Users' ".

There is an unhandled exception i Content Studio that occurs when Content Studio tries to verify a user with the same domain\loginname as an already registered user but with another SID.

This registered user has been removed from Active Directory, NTLM or the local server after that it was registered in Content Studio. Later a user with the same domain\loginname is recreated and this new object is going to be registered Content Studio sees a new user since the internal SID is different from the original one. In this situation Content Studio tries to insert the object and the database refuses this since the combination of domain\loginname must be unique.

Simply unregister the old user from Content Studio.

This is a known error that has been confirmed and will be fixed in later version of Content Studio version 4.