I just tried to mark all topics read for the forums and was given this:

warning: pg_query(): Query failed: ERROR: syntax error at or near "h" LINE 1: DELETE h ^ in /export/drupal/includes/database.pgsql.inc on line 139.
user warning: query: DELETE h FROM history AS h INNER JOIN term_node AS tn ON (h.nid = tn.nid) INNER JOIN term_data AS td ON (td.tid = tn.tid) WHERE h.uid = 240 AND td.vid = 1 in /export/drupal/sites/all/modules/advanced_forum/advanced_forum.module on line 1097.
warning: pg_query(): Query failed: ERROR: duplicate key value violates unique constraint "history_pkey" in /export/drupal/includes/database.pgsql.inc on line 139.
user warning: query: INSERT INTO history (uid, nid, timestamp) SELECT DISTINCT 240, n.nid, 1287821545 FROM node AS n INNER JOIN term_node AS tn ON n.nid=tn.nid INNER JOIN node_comment_statistics AS ncs ON ncs.nid = n.nid INNER JOIN term_data AS td ON tn.tid = td.tid WHERE (n.created > 1285229545 OR ncs.last_comment_timestamp > 1285229545) AND td.vid = 1 in /export/drupal/sites/all/modules/advanced_forum/advanced_forum.module on line 1110.

This happened after I was in General Discussion and had marked all topics read within that section without any problems. I went to the main forum area and noticed that the General Discussion was still registering unread threads, so I went back in, confirmed that there weren't any read ones left, and then went back to the topmost level. I tried marking all posts as read, when that message popped up. I tried a second time and it still gave me the error, and just did it a third time for good measure.

Oh yeah, all the topics are still showing as unread too. It might also help to know that I'm running Chrome right now.