Copying contacts from one address book to another works here if Ctrl is pressed while dragging and dropping, and contact Properties can be edited. If contact or address book edits aren't retained, it's often a sign of a corrupted address book. To test, create a new address book from File/New... and see if contacts can be added from other address books or if a contact in the new book can be edited. If it works, report here for instructions on rebuilding a corrupted address book.