Files with special characters (utf8)

Hi, I am using FCKeditor in MODx cms. Its really great tool for managing files... Thanks a lot for it !!!
But I have a problem with special characters, like ěščřžýáíé. When somebody uploads a file with this character in the name of the file, then whole folder does not work. When I open a folder with one or more files with this bad name... It show an empty folder and gives some JS error node is null.
I hope I can manage it like that: When somebody uploads a file, I wil check its name and replace these bad characters...
In modx filemanager, I hacked it and it works fine, but in FCK, I am not able to do it...
I have tried to hack the file FileUpload.php, in folder connectors.... I manage replacing bad characters when the upload file is moved into the right path...
move_uploaded_file($_FILES['NewFile']['tmp_name'],($this->real_cwd."/$filename($i).$ext"))
But then... it doesnot work... It shows a progress bar, but no progress, no uploading....
Can anybody help me ?? Please....
Thanks lot...
VojtaJina