Index: modules/profile/profile.module
===================================================================
--- modules/profile/profile.module	(revision 724)
+++ modules/profile/profile.module	(working copy)
@@ -263,6 +263,9 @@
 function profile_save_profile(&$edit, $account, $category, $register = FALSE) {
   $result = _profile_get_fields($category, $register);
   foreach ($result as $field) {
+    if (!isset($edit[$field->name])) {
+      continue;
+    }
     if (_profile_field_serialize($field->type)) {
       $edit[$field->name] = serialize($edit[$field->name]);
     }