View filter support for Date field suddenly stopped working on multiple sites

This past week on two completely independent Drupal 5.10 sites of mine the views filter ability has stopped working for me with Date fields. I had views setup to show nodes whose CCK date field was greater than or equal to 'now,' for upcoming events, and on both sites we no longer get any results. If I remove the field from the Filter section of the view then I get all records (of course not filtered by date though).

What I don't get is how without making changes (these sites are not under active development) the bug appeared on both sites.

I was using Date 5.x-2.0-rc7 on both, and have updated (and run update script) to 5.x-2.3 on one to see if the problem is fixed, and it was not.

Using PHP 5.2.5, Drupal 5.10.

Here's the View export:

  $view = new stdClass();
  $view->name = 'training_events';
  $view->description = 'Shows only Training Event calendar_event nodes.';
  $view->access = array (
);
  $view->view_args_php = '';
  $view->page = TRUE;
  $view->page_title = 'Upcoming Training Events';
  $view->page_header = '';
  $view->page_header_format = '1';
  $view->page_footer = '';
  $view->page_footer_format = '1';
  $view->page_empty = '';
  $view->page_empty_format = '1';
  $view->page_type = 'teaser';
  $view->url = 'training-events';
  $view->use_pager = TRUE;
  $view->nodes_per_page = '50';
  $view->block = TRUE;
  $view->block_title = '';
  $view->block_header = '';
  $view->block_header_format = '1';
  $view->block_footer = '';
  $view->block_footer_format = '1';
  $view->block_empty = '';
  $view->block_empty_format = '1';
  $view->block_type = 'list';
  $view->nodes_per_block = '50';
  $view->block_more = TRUE;
  $view->block_use_page_header = FALSE;
  $view->block_use_page_footer = FALSE;
  $view->block_use_page_empty = FALSE;
  $view->sort = array (
    array (
      'tablename' => 'node_data_field_date_time',
      'field' => 'field_date_time_value',
      'sortorder' => 'ASC',
      'options' => '',
    ),
  );
  $view->argument = array (
    array (
      'type' => 'calendar_year',
      'argdefault' => '2',
      'title' => '%1',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
    array (
      'type' => 'calendar_month',
      'argdefault' => '2',
      'title' => '%2',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
    array (
      'type' => 'calendar_day',
      'argdefault' => '2',
      'title' => '%3',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
  );
  $view->field = array (
    array (
      'tablename' => 'node_data_field_date_time',
      'field' => 'field_date_time_value',
      'label' => '',
      'handler' => 'content_views_field_handler_group',
      'options' => 'default',
    ),
    array (
      'tablename' => 'node',
      'field' => 'title',
      'label' => '',
      'handler' => 'views_handler_field_nodelink',
      'options' => 'link',
    ),
    array (
      'tablename' => 'node',
      'field' => 'body',
      'label' => '',
      'handler' => 'views_handler_field_body',
    ),
    array (
      'tablename' => 'node_data_field_contact_name',
      'field' => 'field_contact_name_value',
      'label' => '',
      'handler' => 'content_views_field_handler_ungroup',
      'options' => 'default',
    ),
    array (
      'tablename' => 'node_data_field_location',
      'field' => 'field_location_street1',
      'label' => '',
      'handler' => 'content_views_field_handler_group',
      'options' => 'default',
    ),
  );
  $view->filter = array (
    array (
      'tablename' => 'node',
      'field' => 'status',
      'operator' => '=',
      'options' => '',
      'value' => '1',
    ),
    array (
      'tablename' => 'term_node_2',
      'field' => 'tid',
      'operator' => 'OR',
      'options' => '',
      'value' => array (
  0 => '4',
),
    ),
    array (
      'tablename' => 'node_data_field_date_time',
      'field' => 'field_date_time_value_default',
      'operator' => '>=',
      'options' => 'now',
      'value' => '',
    ),
    array (
      'tablename' => 'node',
      'field' => 'type',
      'operator' => 'OR',
      'options' => '',
      'value' => array (
  0 => 'calendar_event',
),
    ),
  );
  $view->exposed_filter = array (
  );
  $view->requires = array(node_data_field_date_time, node, node_data_field_contact_name, node_data_field_location, term_node_2);
  $views[$view->name] = $view;

If it helps, here's the 'Dev queries' output from the dev module, for this view:

SELECT node.nid, CONCAT(node_data_field_date_time.field_date_time_value,'|',node_data_field_date_time.field_date_time_value2) AS node_data_field_date_time_field_date_time_value, node.title AS node_title, node.changed AS node_changed, node_data_field_contact_name.field_contact_name_value AS node_data_field_contact_name_field_contact_name_value, node_data_field_location.field_location_street1 AS node_data_field_location_field_location_street1, node_data_field_location.field_location_street2 AS node_data_field_location_field_location_street2, node_data_field_location.field_location_apt AS node_data_field_location_field_location_apt, node_data_field_location.field_location_city AS node_data_field_location_field_location_city, node_data_field_location.field_location_state AS node_data_field_location_field_location_state, node_data_field_location.field_location_zip AS node_data_field_location_field_location_zip, node_data_field_location.field_location_country AS node_data_field_location_field_location_country, node_data_field_location.field_location_other AS node_data_field_location_field_location_other, node_data_field_date_time.delta, node.type FROM {node} node LEFT JOIN {term_node} term_node ON node.nid = term_node.nid LEFT JOIN {term_hierarchy} term_hierarchy ON term_node.tid = term_hierarchy.tid LEFT JOIN {content_field_date_time} node_data_field_date_time ON node.vid = node_data_field_date_time.vid LEFT JOIN {content_type_calendar_event} node_data_field_contact_name ON node.vid = node_data_field_contact_name.vid LEFT JOIN {content_type_calendar_event} node_data_field_location ON node.vid = node_data_field_location.vid WHERE (node.status = '1') AND (term_node.tid IN ('4')) AND (DATE_FORMAT(STR_TO_DATE(node_data_field_date_time.field_date_time_value, '%Y-%m-%%dT%T'), '%Y-%m-%%d\T%H:%i') >= '2008-09-28T22:49') AND (node.type IN ('calendar_event')) AND ((STR_TO_DATE(node_data_field_date_time.field_date_time_value2, '%Y-%m-%%dT%T') >= '2008-01-01 00:00:00' AND STR_TO_DATE(node_data_field_date_time.field_date_time_value, '%Y-%m-%%dT%T') <= '2007-12-31 23:59:59')) ORDER BY node_data_field_date_time_field_date_time_value ASC

Thank you for reading this, let me know if additional info is needed.