Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.892
diff -u -r1.892 user.module
--- modules/user/user.module	3 Feb 2008 19:23:01 -0000	1.892
+++ modules/user/user.module	8 Feb 2008 00:22:07 -0000
@@ -230,7 +230,7 @@
           $query .= "$key = '%s', ";
           $v[] = $value;
         }
-        else if ($key != 'roles') {
+        else if ($key != 'roles' && $key != 'form_build_id') {
           // Roles is a special case: it used below.
           if ($value === NULL) {
             unset($data[$key]);