? username_check_caseinsensitive.patch
Index: username_check.unique.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/username_check/username_check.unique.inc,v
retrieving revision 1.3
diff -u -p -r1.3 username_check.unique.inc
--- username_check.unique.inc	13 Jan 2009 13:29:58 -0000	1.3
+++ username_check.unique.inc	16 Jul 2009 18:03:31 -0000
@@ -52,5 +52,5 @@ function username_check_callback() {
  * Query user table to check if such username is already exists.
  */
 function _username_check_is_user_exists($username) {
-  return db_result(db_query("SELECT COUNT(u.name) FROM {users} u WHERE u.name = '%s'", $username));
+  return db_result(db_query("SELECT COUNT(u.name) FROM {users} u WHERE LOWER(u.name) = LOWER('%s')", $username));
 }