The module User Management could not be loaded

Hello I just wanted to change some setting of the users of the system. But when I try to access the user management via the KDE control center I obtain the following error message: (Using Kubuntu 10.04 and the latest trinity package) ,---- | | The module User Management could not be loaded. | Possible reasons: | * An error occurred during your last kde upgrade leaving an orphaned control module | * You have old third party modules lying around | | Check these points carefully and try to remove the module mentioned | in the error message. If this fails, consider contacting your distributor | or packager. `---- Which package is missing? Thanks Uwe Brauer