Just like using the <base> tag into web pages, CKEditor can now be configured to use a specific URL as the "base" to resolve the address of other resources, like images. This is extremely useful when using the editor to manage pages that will be running in different domains or in different parts of the site. See baseHref in the API docs.
Re: Problem with image links (FCK)
new CKEditor v3.1exactly
in the documentation