Index: user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user.module,v
retrieving revision 1.454.2.22
diff -U3 -r1.454.2.22 user.module
--- user.module	13 Mar 2006 21:29:18 -0000	1.454.2.22
+++ user.module	26 Apr 2006 23:29:35 -0000
@@ -814,6 +814,10 @@
       user_module_invoke('login', $edit, $user);
 
       $old_session_id = session_id();
+      // destroy the cookie on the client to prevent the existence of two domain cookies
+      if (isset($_COOKIE[session_name()])) {
+        setcookie(session_name(), '', time()-42000, '/');
+      }
       session_regenerate_id();
       db_query("UPDATE {sessions} SET sid = '%s' WHERE sid = '%s'", session_id(), $old_session_id);