Just been through this myself. Key was to to place an error handler around the PHP FckEditor FileUpload function where the famous "move_uploaded_file" function call is located. For me it was a permissions issue such that the process under which php runs did not have write permission into my web server owned destination file directory. So as I dont have admin to the server I had two options, give enough permissions such that php could write to it (start with full and prove it works) then wynd it back OR secondly use PHP ftp functions to copy the file from its temp location to the wed server owned directory. They key is to use the same ftp user you use to upload your web content.