You will get this message if your server is not running CEE 5.0 or greater. It simply means that some features will not be available. For example, you must be on CEE 5.0 for required fields to be validated in the rich editor. If you are on an earlier version, they are validated on the server and an error message is returned. Essentially, the user interface is cleaner when the newer version is used.
For more information and to get the latest version see: CollabNet Desktop Downloads