Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.892.2.8
diff -u -p -r1.892.2.8 user.module
--- modules/user/user.module	8 Oct 2008 20:12:18 -0000	1.892.2.8
+++ modules/user/user.module	31 Oct 2008 14:10:48 -0000
@@ -482,7 +482,7 @@ function user_access($string, $account =
   static $perm = array();
 
   if ($reset) {
-    unset($perm);
+    $perm = array();
   }
 
   if (is_null($account)) {