--- modules/user/user.module	2010-11-04 02:16:45.000000000 -0700
+++ modules/user/user.module	2010-12-02 11:45:43.557493816 -0800
@@ -2481,7 +2481,7 @@
     unset($form['account']);
   }
   else {
-    $form = array_merge($form, $extra);
+    $form = array_merge_recursive($form, $extra);
   }
 
   if (variable_get('configurable_timezones', 1)) {