Index: form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.265.2.32
diff -u -p -r1.265.2.32 form.inc
--- form.inc	1 Mar 2010 09:24:22 -0000	1.265.2.32
+++ form.inc	27 Oct 2010 15:15:10 -0000
@@ -2274,6 +2274,7 @@ function form_clean_id($id = NULL, $flus
     return;
   }
   $id = str_replace(array('][', '_', ' '), '-', $id);
+  $id = preg_replace('/[^\x{002D}\x{0030}-\x{0039}\x{0041}-\x{005A}\x{005F}\x{0061}-\x{007A}\x{00A1}-\x{FFFF}]/u', '', $id);
 
   // Ensure IDs are unique. The first occurrence is held but left alone.
   // Subsequent occurrences get a number appended to them. This incrementing