401 error on iis when uploading files via PHP

I have an upload script that runs on a windows webserver 2008. The uploads works nice, the file is created on the server. But when I try to access the uploaded image file via http, I just get an error 401. How can I resolve this?

EDIT: setting the chmod to 0777 after the file has been uploaded did not help, too.

Answer

That did it: https://serverfault.com/questions/85983/iis-iusrs-cannot-access-files-uploaded-and-created-by-network-service-error-401/229151#229151