Symptom
If a client with managed Classic preferences tries to use the Extensions Manager, File Sharing, or Software Update control panels, she sees an alert box with a message that says:
"The operation could not be completed. An unexpected error occurred (error code 1016)."
Solution
This message indicates that an Admin user has restricted access to the item you tried to use. Non-Admin users may not use these control panels when Classic preferences are managed. You may also see the message if the Admin has selected "Hide Chooser and Network Browser" in Workgroup Manager.
The message also appears if you try to open an unapproved application (one that is not listed in the Items pane of the Applications preference in Workgroup manager) in either Classic or Mac OS X.