Translations:Manual:Image authorization/114/en

There have been several articles and hints that some versions of IIS may disallow the server variables PATH_INFO and PATH_TRANSLATE 'for security reasons'. While we did not have this problem on the current server and patch level (IIS 6.0) it is a noted issue for IIS 4.0 (and possibly prior), you may want to investigate if img_auth.php is not working for you.