Thank you for your reply.
"title of the modules" you explained means "course name" ?
Yes, I am not using these characters for a course name. And I can download Excel format file. When I download only Text format file, the file name is changed to string like a URL. (I can download quiz result report in Text format.)
I thought clean_filename function in course/grades.php has a bug but on another test site I can download Text format grade file. A difference of these two is WWW server(IIS,Apache) and Moodle version(1.3, nighty) and Windows ( IIS run on Win2kServer , Apache run on WinXP). Both site is running in Japanese. I checked in another language setting for a course.