The Database Navigator and Object Editors load their objects "lazy" - this means that schema information will not be fetched from the server unless you "ask" for it. This is especially helpful when working on low-bandwidth connections, like an ISDN dialup line. If you're on a Local Area Network (LAN) and you would like to avoid this behaviour, check the Database Registration Options - there's an option to load all schema objects right after establishing the connection.
After loading an object, Database Workbench keeps this cached and will not reload any objects until you either click the Refresh From Database button in the Database Navigator, or use Refresh from any of the context sensitive menus available in the Database Navigator.
The Refresh buttons in the Database Navigator
Note:
Database Workbench will not detect any changes to objects done by other developers on the same database after having loaded the object properties.