Why on earth would you want to update the object key? If you are able to update it through Site Administration, then I would say it is a bug. LK_OBJECT_KEY is part of the primary key for the table, so you should not be able to change it.
In the DB reference for ALM 11.0 you can read this about the LOCKS table:
"Locks to control access to the same item by different user sessions. For internal use. Do not change values in this table."
I use deletions on this table when users get a crash and have their own user ID locking them out. But updating it does not make sense in my opinion.