Check Drupal fields for corrupt data https://drupal.org/node/1185368

drupal_write_record

<?php
  // *********** Print $fields array to investigate which field content are problematic
  print_r($fields);

  // Build the SQL.
  if (empty($primary_keys)) {
    // We are doing an insert.
    $options = array('return' => Database::RETURN_INSERT_ID);
?>