Index: wp-admin/includes/misc.php
===================================================================
--- wp-admin/includes/misc.php	(revision 17321)
+++ wp-admin/includes/misc.php	(working copy)
@@ -148,7 +148,10 @@
  *
  * @return bool True if web.config was updated successfully
  */
-function iis7_save_url_rewrite_rules(){
+function iis7_save_url_rewrite_rules() {
+	if ( is_multisite() )
+		return;
+
 	global $wp_rewrite;
 
 	$home_path = get_home_path();