fckeditor error

In addition to the above fix suggestions, I'm not sure how much freedom you have over the editor or how much of an overhead it would be for you to upgrade, but if it's feasible you may want to upgrade to the latest version of CKEditor instead (the name was changed at v3). I've personally found lots of little bugs/cross-browser compatibility issues with legacy sites using FCKEditor which have been quickly fixed with a simple update. See http://ckeditor.com for a demo and download.

Possibly a locale/encoding issue. The file path appears to be in Turkish(?). Test with a file path composed of exclusively US/English characters to see whether that is the cause.

You'll need to adjust the fckeditor configuration file on the server. For more info on that you should go to the wiki on the fckeditor website. Though I'll tell you that using the file uploader in fckeditor does pose some server security risk.