Problems uploading large filenames and with special characters

I am using the version 2.3.3 of Moodle for Windows. It is installed on Windows 2003 Server and IIS with mysql 5.5.

When I try to upload a file to a course with a long filename or special characters I can uploaded (apparently) but after that when I try to access to the file I got an error.

Please its important for us not to change the filenames; I am loosing a lot of time trying to fix this...

Could somebody help me please!!!

Thanks in advance

Cristina