Error when saving sort order of "sortable grid"

This error message has been diplayed:

PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect integer value: '' for column 'nid' at row 1: INSERT INTO {sgrid} (nid, rank, view_display) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2); Array ( [:db_insert_placeholder_0] => [:db_insert_placeholder_1] => 0 [:db_insert_placeholder_2] => component_map_page ) in sgrid_view_sgrid_form_submit() (line 73 of /Applications/MAMP/htdocs/map drupal-7.14/sites/all/modules/sgrid/sgrid.module).

Moving elements around works, logged in as admin user #1.
Drupal 7.14

Cheers
Rolf