Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.1224
diff -u -r1.1224 user.module
--- modules/user/user.module	30 Nov 2010 23:55:11 -0000	1.1224
+++ modules/user/user.module	10 Dec 2010 14:45:41 -0000
@@ -1191,7 +1191,7 @@
     if ($error = user_validate_mail($form_state['values']['mail'])) {
       form_set_error('mail', $error);
     }
-    elseif ((bool) db_select('users')->fields('users', array('uid'))->condition('uid', $account->uid, '<>')->condition('mail', db_like($form_state['values']['mail']), 'LIKE')->range(0, 1)->execute()->fetchField()) {
+    elseif ((bool) db_select('users')->fields('users', array('uid'))->condition('uid', $account->uid, '<>')->condition('mail', db_like(trim($form_state['values']['mail'])), 'LIKE')->range(0, 1)->execute()->fetchField()) {
       // Format error message dependent on whether the user is logged in or not.
       if ($GLOBALS['user']->uid) {
         form_set_error('mail', t('The e-mail address %email is already taken.', array('%email' => $form_state['values']['mail'])));