I also had this issue. For now I put a warning on the upload page not to use
This is not a very good solution...
Windows doesn't have any problem handling special characters in file names.
But either MediaWiki or PHP are mangling the file name somehow before
writing it. And the file name mangling used to create the file on the file
system is different from the one used later on the URL. That's why the file
is not found.
Possible solutions would be:
a) To discover who is changing the file name (MediaWiki or PHP) and try to
b) To put some code on the upload file form that, when running under
Windows, would suggest a safe file name.
I might try to do this in the future if there is a chance the patch would be
accepted for MediaWiki.