This error occured on my workspace
user error: Unknown column 'n.nid' in 'on clause'
query: SELECT n.nid, n.uid, n.type, 0 AS cid, n.title, n.status, n.changed, s.comment_count, 1 AS node FROM node n LEFT JOIN node_comment_statistics s ON n.nid = s.nid WHERE n.uid = 33 UNION SELECT c.nid AS cnid, c.uid, "" AS type, c.cid, c.subject, c.status, c.timestamp, c.pid, 0 FROM node n, comments AS c LEFT JOIN node_comment_statistics s ON n.nid = s.nid WHERE c.uid = 33 ORDER BY changed DESC LIMIT 0, 50 in /home/.devil/eglug/eglug.org/includes/database.mysql.inc on line 66
According to this I found that we need to change the order of the tables to:
SELECT c.nid AS cnid, c.uid, "" AS type, c.cid, c.subject, c.status, c.timestamp, c.pid, 0 FROM min_comments AS c, min_node n LEFT JOIN min_node_comment_statistics s ON n.nid = s.nid WHERE c.uid = 1 ORDER BY changed DESC LIMIT 0, 50
It might be work. try to test it admins

fixed
alright, looks like this problem was present since we moved hosts because they use MySQL 5 (or they upgraded a few days ago, silently?) which has some SQL syntax changes, The fix you included does indeed work, however, according to MySQL 5 SQL changes which are documented here, all what was needed is a couple of braces.
PS: Thanks for the link, saved me time ;-)