Search Unknown Column 'INF' in 'field list'; Search Fails

Any search is failing, and is showing the following failure:

    * user warning: Unknown column 'INF' in 'field list' query: CREATE TEMPORARY TABLE temp_search_results SELECT i.type, i.sid, 5 * (50.73595434091 * i.relevance) + 5 * POW(2, (GREATEST(n.created, n.changed, c.last_comment_timestamp) - 1172979726) * 6.43e-8) + 5 * (2.0 - 2.0 / (1.0 + c.comment_count * 1)) + 5 * (2.0 - 2.0 / (1.0 + nc.totalcount * -INF)) AS score FROM temp_search_sids i INNER JOIN search_dataset d ON i.sid = d.sid AND i.type = d.type INNER JOIN node n ON n.nid = i.sid LEFT JOIN node_comment_statistics c ON c.nid = i.sid LEFT JOIN node_counter nc ON nc.nid = i.sid WHERE (d.data LIKE '% openvms %') ORDER BY score DESC in /Library/WebServer/Documents/drupal/includes/database.mysql.inc on line 172.
    * user warning: Table 'db.temp_search_results' doesn't exist query: SELECT COUNT(*) FROM temp_search_results in /Library/WebServer/Documents/drupal/includes/database.mysql.inc on line 172.

Drupal 5.1. Add-on modules include Captcha 5.x-1.1, Text Image 5.x-1.2, Site menu 5.x-1.x-dev and Bloginfo 5.x-1.0.

The search status reports completely indexed, and cron has been run.

Various Google and Drupal searches turn up no similar keywords and no previous similar discussions here at Drupal.org.

This had been working recently, and no recent obvious changes nor obvious triggers come to mind for this error.

I'm presently digging around to see if I can figure out where this INF came from.