Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.1179
diff -u -r1.1179 user.module
--- modules/user/user.module	29 Jun 2010 18:24:10 -0000	1.1179
+++ modules/user/user.module	6 Jul 2010 23:40:41 -0000
@@ -574,7 +574,7 @@
  * Verify the syntax of the given name.
  */
 function user_validate_name($name) {
-  if (!$name) {
+  if (!strlen($name)) {
     return t('You must enter a username.');
   }
   if (substr($name, 0, 1) == ' ') {