These's have been a few of the error messages I've come across using the Domino User Connector.
Error: CTGDKC065E Unable to execute Domino Action. NotesException occurred: ID=4,005, Error Text=Notes error: You are not allowed to update the certifier log (Smith)
Cause: 'REG_RegistrationServer' value is wrong
Error: CTGDKC065E Unable to execute Domino Action. NotesException occurred: ID=4,000, Error Text=Notes error: The prompt for password was aborted by user
Cause: 'REG_CertPassword' value is wrong
Error: CTGDKC002E Failed to execute the command. NotesException occurred: Notes error: Unable to find path to server. Check that your network connection is working. If you have a working connection, go to Preferences - Notes Ports and click Trace to discover where it breaks down. (adtdi/ibm!!mail\msmith.nsf)
Cause: 'REG_Server' value is wrong