[kgroneman]

That did it! Thanks to you both! This now works.

SELECT count(vb_post.postid) AS vb_postcount, vb_user.username
FROM vb_post AS vb_post
LEFT JOIN vb_user AS vb_user ON (vb_user.userid = vb_post.userid)
LEFT JOIN vb_thread AS vb_thread ON (vb_thread.threadid = vb_post.threadid) 
WHERE vb_post.dateline > UNIX_TIMESTAMP(DATE_SUB(CURDATE(), INTERVAL 1 MONTH))
AND vb_thread.forumid NOT IN (10,588,589,591,592,593,594,595,597,599,601,608,609,641,644,645,646,647,649,650,652,654,671,689,737,739,740,741,782,783,1228,1229,1230,1231,1232,1233,1234,1235,1236,1237,1239,1240,1241,1242,1274,1275,1278,1279,1280,1289,1290,1292)
GROUP BY vb_post.userid
ORDER BY vb_postcount
DESC

I owe you guys...and so fast on the replies! I'm amazed and thankful.