Been walking through --a very long walk I might add-- a lot of suggested solutions but never found one that would address my problem.
I kept on getting the same response:
The server didn't send back a proper
XML response. Please contact your
system administrator.
XML request error: OK (200)
Requested URL:
https:.../fckeditor/editor/filemanager/connectors/aspx/connector.aspx?Command=GetFoldersAndFiles&Type=Image&CurrentFolder=%2F&uuid=1260177467559
Response text:
window.location.replace("http:.../fckeditor/editor/filemanager/connectors/aspx/connector.aspx?Command=GetFoldersAndFiles&Type=Image&CurrentFolder=%2F&uuid=1260177467559
Until finally, I stepped closer, re-read the response again and noticed that the request and response are using different protocols.
FYI, the editor is implemented in a secure part of the site accessible by site admins only. We're using the Ventaur component that does the automatic switching of HTTP/HTTPS requests.
The images --we only need to upload/browser image types-- reside in a subdirectory that is also configured to use HTTPS.
This gave me an indication as to where the problem is coming from, so I proceeded to set the fckeditor directory to use HTTPS as well.
This finally worked and iI was able to upload/browse images.